Hi Praveer,
I have tried this
if itab-gesc1 ne space.
perform bdc_field using 'Q0021-GESC2'
''.
perform bdc_field using 'Q0021-GESC1'
'X'.
elseif itab-gesc2 ne space.
perform bdc_field using 'Q0021-GESC2'
'X'.
perform bdc_field using 'Q0021-GESC1'
''.
endif.
which I hope is equivalent to what you said and even this not works.
Regards
Nav