I want to write a visual app that will replace phone dialer, so that when filemaker passes a phone number to phone dialer it is actually passing the information into my application. I need to know HOW filemaker gives this information to phone dialer??? Or do you know a way i can make phone dialer invisible?:

I doubt that anyone except FMI knows what Filemaker does internally. I would guess that your best chance is to write a plugin (or find one) that does the dialing. Then it becomes irrelevant as to what FM does. Filemaker Advisor had an article by Peter Baanen (Troi) in this Sept. issue about writing plugins.