MB0A - BDC issue

Hi Gurus

Due to some strainge reasons I had to use BDC for Tr. MB0A... Its going thru 3 screens...all the data is populating well and finally its coming to Screen BDC_dynpro SAPMM07M' '0221' where all the field are not editable, and I had to do is Hit save there....

I populated my table saying

PERFORM bdc_field USING 'BDC_OKCODE'

'=BU'. But it doesn't save

I tried all options of all screen modes and update modes... I am not finding a solution.. I even tried using menu path to save, even then it doesn't save, Can some one help.....Thanks.