Well, one way maybe to create a simple batch file that runs your actual script and the first line in that batch file may be to check for existence of a ps1 in your update folder. If there is one, it can copy it down first, and then start your powershell script
Eg. whenever there is an update, you put your 'Mypowershellscript.ps1' script in c:\temp\update\ folderc:\temp\update\ folder
and let's assume your script will be running from c:\temp\myscriptfolder
then
c:\temp\myscriptfolder\ then you can create batch file like this
if NOT exist C:\temp\update\mypowershelscript.ps1 goto :end
copy /Y c:\temp\update\MyPowerShellScript.ps1 c:\temp\MyScriptFolder\
:END
%systemroot%\System32\WindowsPowerShell\v1.0\powershell.exe -nologo -noprofile -file "c:\temp\myscriptfolder\mypowershellscript.ps1"
if NOT exist C:\temp\update\mypowershelscript.ps1 goto :end copy /Y c:\temp\update\MyPowerShellScript.ps1 c:\temp\MyScriptFolder\ :END %systemroot%\System32\WindowsPowerShell\v1.0\powershell.exe -nologo -noprofile -file "c:\temp\myscriptfolder\mypowershellscript.ps1"