G/L validation on Ztable in FB60.

Hi Experts,

I have a requirement in the Tcode 'FB60'.

i have created a ztable for G/L account and its permission, when user enter G/L in FB60 it should validate with the ztable and if not permitted it should THROW a ERROR msg that 'ENTER INTERNAL ORDER'.

I am not getting with which i should proceed EXIT,BADI,BTE or OB28 which will fullfill my requirement.

can badi 'BADI_FDCB_SUBBAS04' WILL BE USEFULL I CHECKED IN SUBBAS01 but G/L IS NOT VISIBLE FOR fb60.

PLZ HELP

Thanks

Rahul