Autorun Excel vba code when cell value changes [duplicate]

Let's start with this code, which I will explain below.

Open the VB Editor Alt+F11. Right click the sheet that you want this behavior to occur on and select View Code.

Copy and paste the following code into the worksheet code.

Private Sub Worksheet_Change(ByVal Target As Range) 'CountLarge is an Excel 2007+ property, if using Excel 2003 'change to just Count If Target.Cells.CountLarge > 1 Or IsEmpty(Target) Then Exit Sub If Target.Address = "$A$1" Then If Target.Value = 0 Then Me.Range("H32").FormulaR1C1 = "=SUM(R[-4]C:R[-2]C)" ElseIf Target.Value = 1 Then Me.Range("B15").FormulaR1C1 = "=SUM(R[-1]C:R[-1]C)" End If End If End Sub 

The Worksheet_Change event is fired every time a user makes a change to the worksheet. If you change a cell value, for example, this event is triggered.

The first line within this subroutine checks to ensure that multiple cells weren't changed and that there was in fact an actual cell change, if either is not true then it will not continue.

Then we check to ensure that the value change happened in cell A1, if it did, we enter that IF statement.

From there, we check the value that was entered into cell A1. If the value was 0, the appropriate formula is added to H32. If the value was 1, the appropriate formula is added to B15. If a value other than 0 or 1 is entered into cell A1, nothing happens.

It is important to note that you must leave the cell for this event to trigger, so while this is a good start, I don't currently know of a way to get this event to fire without at least pressing enter or leaving the cell.

Update

After a bit of research and playing around, I've figured out how you can make this change without pressing enter or any other button, this will occur immediately after either '0' or '1' is pressed, even if you are editing the cell value. I used a keyboard handler from this previous SO question.

The code between the BEGIN KEYBOARD HANDLING and END KEYBOARD HANDLING event was from above.

Copy and paste the following code into the worksheet code of whichever sheet you want to capture these key strokes on:

Option Explicit 'BEGIN KEYBOARD HANDLING Private Type POINTAPI x As Long y As Long End Type Private Type MSG hwnd As Long Message As Long wParam As Long lParam As Long time As Long pt As POINTAPI End Type Private Declare Function WaitMessage Lib "user32" () As Long Private Declare Function PeekMessage Lib "user32" _ Alias "PeekMessageA" _ (ByRef lpMsg As MSG, ByVal hwnd As Long, _ ByVal wMsgFilterMin As Long, _ ByVal wMsgFilterMax As Long, _ ByVal wRemoveMsg As Long) As Long Private Declare Function TranslateMessage Lib "user32" _ (ByRef lpMsg As MSG) As Long Private Declare Function PostMessage Lib "user32" _ Alias "PostMessageA" _ (ByVal hwnd As Long, _ ByVal wMsg As Long, _ ByVal wParam As Long, _ lParam As Any) As Long Private Declare Function FindWindow Lib "user32" _ Alias "FindWindowA" _ (ByVal lpClassName As String, _ ByVal lpWindowName As String) As Long Private Const WM_KEYDOWN As Long = &H100 Private Const PM_REMOVE As Long = &H1 Private Const WM_CHAR As Long = &H102 Private bExitLoop As Boolean Sub StartKeyWatch() Dim msgMessage As MSG Dim bCancel As Boolean Dim iKeyCode As Integer Dim lXLhwnd As Long 'handle the ESC key. On Error GoTo errHandler: Application.EnableCancelKey = xlErrorHandler 'initialize this boolean flag. bExitLoop = False 'get the app hwnd. lXLhwnd = FindWindow("XLMAIN", Application.Caption) Do WaitMessage 'check for a key press and remove it from the msg queue. If PeekMessage _ (msgMessage, lXLhwnd, WM_KEYDOWN, WM_KEYDOWN, PM_REMOVE) Then 'strore the virtual key code for later use. iKeyCode = msgMessage.wParam 'translate the virtual key code into a char msg. TranslateMessage msgMessage PeekMessage msgMessage, lXLhwnd, WM_CHAR, _ WM_CHAR, PM_REMOVE 'for some obscure reason, the following 'keys are not trapped inside the event handler 'so we handle them here. If iKeyCode = vbKeyBack Then SendKeys "{BS}" If iKeyCode = vbKeyReturn Then SendKeys "{ENTER}" 'assume the cancel argument is False. bCancel = False 'the VBA RaiseEvent statement does not seem to return ByRef arguments 'so we call a KeyPress routine rather than a propper event handler. Sheet_KeyPress _ ByVal msgMessage.wParam, ByVal iKeyCode, ByVal Selection, bCancel 'if the key pressed is allowed post it to the application. If bCancel = False Then PostMessage _ lXLhwnd, msgMessage.Message, msgMessage.wParam, 0 End If End If errHandler: 'allow the processing of other msgs. DoEvents Loop Until bExitLoop End Sub Sub StopKeyWatch() 'set this boolean flag to exit the above loop. bExitLoop = True End Sub Private Sub Worksheet_Activate() Me.StartKeyWatch End Sub Private Sub Worksheet_Deactivate() Me.StopKeyWatch End Sub 'End Keyboard Handling Private Sub Sheet_KeyPress(ByVal KeyAscii As Integer, ByVal KeyCode As Integer, ByVal Target As Range, Cancel As Boolean) 'CountLarge is an Excel 2007+ property, if using Excel 2003 'change to just Count If Target.Cells.CountLarge > 1 Or IsEmpty(Target) Then Exit Sub If Target.Address = "$A$1" Then If KeyAscii = 48 Then Me.Range("H32").FormulaR1C1 = "=SUM(R[-4]C:R[-2]C)" ElseIf KeyAscii = 49 Then Me.Range("B15").FormulaR1C1 = "=SUM(R[-1]C:R[-1]C)" End If End If End Sub 

Additionally, right click on the ThisWorkbook object --> View Code, and add this code in:

Private Sub Workbook_Open() Sheets("Sheet1").StartKeyWatch End Sub 

Be sure to change Sheet1 to whatever the name of your worksheet is.

The VBA will 'listen' for key presses and if the active cell is A1 and either a 0 or 1 is entered, the appropriate action will be performed even before the user does anything else.

I will add that his comes at a slight performance cost, as the code that executes on Workbook_Open takes a couple seconds to run.

Thanks to user Siddharth Rout for pointing out the potential issue with Count from Excel 2007 and on and directing me to use CountLarge instead.