A pulse 100 times a second equates to a pulse every 10 ms.
At default X2 clock speed (8 MHz) the chip will execute approximately 40 BASIC instructions. Note commands some such as GOSUB, RETURN, take a little longer as there are greater overheads.
If you establish the interrupt with SETINT then you will also need a subroutine called/labelled Interrupt: to handle the action.
This subroutine must also re-enable the interrupts prior to the RETURN command so you will need a new SETINT within the Interrupt: subroutine.
The time you spend in the Interrupt: subroutine, you may miss any other interrupt signals coming from the push button switch on input pin C.2.
For that reason you should do the minimum processing in the interrupt subroutine, just identify what is the source of the interrupt and set a flag (variable) that the main program loop will use to perform consequent actions.
If there is a prospect that there could be a back –log with pulses coming faster than being handled, for the flag increment the value in the Interrupt: subroutine each time a pulse is received. Then in the main program decrement the flag/counter variable each time the required action is undertaken.
Without a lot more details about what the required functionality of your program/project is it is difficult to give specific information.