SAP CATS add time sheet records

Before a user gets his timesheets in online CATS application where he can book his hours i need to add additional lines to the screen fields, these extra lines come out of a external application.

So i want to display the extarnal application timesheet lines in the standard CATS sceen so all checks will be carried out when the user presses the check button.

Someone know how / where to do this??

Grtz Richard

P.s. maybe this is not the right forum but i could not find a specific CATS forum!