BDC for FB09

Hello,

I am trying to update 2 specific fields using FB09 by giving document number, co.code and year.

But when I record using shdb I am getting different screen for different document screen numbers ,because of which BDC is failing.

The screen numbers I am getting is 300 , 303 and 304 in different scenarios.

Now, what i want is whatever may be the screen number, I want my cursor to be positioned at a particular field which is to be updated.

Can anyone guide me in doing this?

Thanks & Regards

Raj