This is one way to do it.
Date/Time: Save "hh:mm" into %T1%
If Variable %T1% >= "hh:mm"
AND
If Variable %T1% <= "hh:mm"
Macro Stop
Example:
Date/Time: Save "hh:mm" into %T1%
If Variable %T1% >= "12:00"
AND
If Variable %T1% <= "13:00"
Macro Stop
The macro will check system time and if it's between 12:00 and 13:00 it will stop the macro.
Edit the interval to suit the lenght of the macro.