FF_5 User Exit to calculate tax automatically.

Hi Guys,

The postings in FF_5 are done through transaction FB01 in the background. There is no way the user can enable the Calculate tax automatically (BSEG-XMWST)check box in the background. I would like to know if there are any appropriate user exit or BTE to use to enable me to tick that check box for certain conditions, e.g. specific GL accounts (BSEG-HKONT) and document types (BKPF-BLART). I tried BTE's 1020 and 1120, but they are not working. I'm guessing they are implemented too far into the process that they are not effective.

Please assist.

Regards,

Darlington