finish a MIPS program

I have started a MIPS program but need help finishing it. I need to add an interrupt service routine (ISR) to an existing program. The program, which is a fully functional hexadecimal counter that shows the current counter value on the seven-segment display already works. But I need help with using the timer to generate an interrupt every x cycles (where x can be between 100 and 200 cycles). The ISR needs to do the following things: 1. Toggle all eight LEDs (i.e. if they are all off, they should all be turned on and if they are already on, turn them off) 2. Perform any tasks necessary to allow another timer interrupt within 100 to 200 cycles. No changes should be made to the existing main loop or sseg_display.asm. Code should only be added following the TODO comments