Web Dynpro ALV grid on_data_check event not triggering

Hello,

I have the following scenarios for the on_data_check event in my web dynpro alv grid :

1) it gets triggerred when i change data in my alv then click "check"

2) it gets triggerred when i change data in my alv then click "enter" then click "check"

3) it gets triggerred when i enter a filter value then change data in my alv then click "check"

4) it doesn't gets triggerred when i enter a filter value then change data in my alv then click "enter" then click "check"

Please advise why it wouldnt get triggered in the fourth case which is identical to the second case above except that there is a filter active. Also, the fourth case is identical to the third case except for the clicking of "enter" before the check.

It would also be nice to know the exact relationship between clicking the "check" button and the "on_data_check" event so that I can understand a bit better.

Many thanks in advance!

Samir