Using SQL Function Results in other SQL Functions

Hi

Can i call a SQL Function with the Values that i got back as a Result from another SQL Function?

fn_GET_USER(KEY) -> gives me back 3 Values (APPLICATION, ZONE, DEALER) that i'd like to use in fn_REPORT_SOURCE(APPLICATION, ZONE, DEALER)

to get a Dealer-Hierarchy list that i'll use in a Dropdown-Menu.

I tried with Parameters, but i'm reading that their Static.

Thanks

Best Regards

-Boris