Get Migo Field values

Hello

I added a custom screen in Migo Item detail

the fields are populated and the tab is shown.

Requirement is to update the mseg table with these values.(I have already created an append structute to table mseg with these fields ZEX and ZID.)

Problem:

I am not able to get these fields in Bapi of MIGO.

weather I am in the

IF_EX_MB_MIGO_BADI~LINE_MODIFY

~PBO_DETAIL

or ~POST_DOCUMENT

I am unable to get them,

Get parameter id 'ZID' field data(zid). does not work,even though the screen in the custom program has parameter,somehow in migo is without one.

The line I save it with a global parameter g_line_id and works okay.

how can I get these two values ?

Thank You in advance