Addition New conditions into me21 programatically

Hi Friends,

I am struck with the adding New Condition Records into the ME21 (Purchase Order).

The requirement is:

Adding a button on the screen to get User-Condition Record (1-Record).    (Say, Condition Type / Value / Currency / Unit )

And upon submitting a button, the above {single} record should automatically be posted to the Condition Tab of every Line-Items.

I have done the Above Screen and tried to post the records also using the below routine:

                      Main-Include : RV61AFZB                       FORM  : USEREXIT_XKOMV_BEWERTEN_INIT.

Currently I am trying to manipulate the XKOMV internal table. from the above routine.

But I am failing to achieve the functionality.

*****Note: This all should happen before SAVE.  Once the uesr finds ok, then, he will save it.

Can anyone help me on, where to add the code ?

Thanks and Advance,

-Ramani Nagarajan