Defalting start time and end time based on absence type selected

Dear all,

Greetings.

I have a doubt in ESS leave request .i will just brief my scenario.

We have 6 absence type CL first half leave and CL second half leave and 4 more .when user will select these absence

type in leave request according to that start time and end time should get defaulted automatically .I try to  badi PT_ABS_ARQ

but all methods triggers only after clicking on review button.Please give me some hints .I need a BAdI which triggers after selecting absence type

Waiting for your valuable inputs.

Thanks.