Hey Ali,
To make your own pulse width modulated signal use two timers where one timer acts like the period and then the second timer acts like the pulse width. Looks something like:
Trigger Pulse Period (Ti) On-Delay
|--||--------------------( )--|
Pulse Period Pulse Width (Ti) Off-Delay
|--||--------------------( )--|
Pulse Width Pulse Period
|--||--------------------(R)--|
When the trigger is activated it turns on the period timer when activates the pulse width timer, when pulse width timer shuts off so does the output. The pulse period rest coil resets the pulse period timer which starts the sequence over again. To get the desired ON/OFF times you load the counters with a value, eg to get a 50% duty cycle, load pulse period with 1 second and then load pulse width with 500ms. Enjoy.
-Kris Kizlyk