DOWN PAYMENT AZWR in sales invoice

Hi,

When I m creating a sales invoice VF01, the system retrieves  the Down payment settlement from F-29.

I would to like to know how to change the amount of condition type AZWR ( down payment) directly in the invoice.

Is it possible to choose the amount?

For example /

I have done a down payment settlement of 300 EUROS, then in the invoice I would like to take only 150 euros, and take 150 euros in an other invoice.

Thank for any help

Rgds

Kari