Suppose I have a process that follows an arithmetic brownian motion

$dX_t = \sigma dW_t$

How do I calculate, within a certain interval $\Delta t$
, the expected number of times that the process will "leave" a certain band $\delta$
 from the starting time.

I.e, suppose I have a starting point $X_0$
 and $t_0$
. Suppose that by $t_1,X_1>X_0+\delta$
 or $X_1<X_0−\delta $
. This should add one to the count. Then I want to reset the band to $X_1±\delta$
 etc. What are the expected number of times that the process $X_t$
 will leave these bands within $\Delta t$?

Otherwise said, if I'm repetitively buying double barrier knock-in options on successive fills on an ABM, how many times should I get hit within a certain time interval.