Simple Timer question

Hello everyone
I failed miserably to get my head round HSERIN/HSEROUT yesterday so I am trying a new approach. I really need some background timer running so that I can set a time out a bit like this:

Main:

if portb.0 = 1 then gosub dostuff 'a pin gets waggled

'if 3 minutes is up then do something here

goto main


gosub dostuff

'reset the timer back to 0

return

Basically under normal circumstances pins will be going high and low and each time they do I want to set the timer back to zero, it is only if there is inactivity that I want to flag it, but do it in the background while the main code is executing. I have been trying to find a simple timer example that applies to me but can't quite understand what I need.

Thanks

Code:

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INCLUDE "Elapsed.bas"

Gosub ResetTime    ' Reset Time to  0d-00:00:00.00   
Gosub StartTimer  ' Start the Elapsed Timer

Main:
    if portb.0 = 1 then gosub dostuff 'a pin gets waggled
   
    IF MinutesChanged THEN
        MinutesChanged = 0
        IF Minutes = 3 THEN 
          'if 3 minutes is up then do something here
         
            Gosub ResetTime    ' Reset Time to  0d-00:00:00.00   
        ENDIF
    ENDIF
goto main
   
   
dostuff:
    ; waggle as desired
   
    Gosub ResetTime    ' Reset Time to  0d-00:00:00.00   
return

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