Cats webdynpro modification for selecting PS project activities

Dear community,

This is the challange:

Employees need to write their time in CATS webdynpro (ECC6 EHP5) to PS project activities. The employees are assigned to 200+ activities from approx 4 to 5 projects. The worklist in SAP CATS is now to long for the employee due to the 200+ activities.

We want to provide the employee with an user friendly function so he is able to select a project activity from e.g. a drill down menu.

Is there anyone with experience with a simular case or with modifying the CATS webdynpro?