Unable to Update Cost in Mass Additions

Hi,

 We are transferring the CIP assets to  FA for the first time, on the project side set up  under our  Capital Project Type under  capitalization information we have  the following set ups

1.     Group Method = All

2.     Group Supplier Invoices Checked

Due to the above set up all the asset lines are grouped and transferred to FA as One line as New with zero cost and other lines as MERGED.

Now if I post the mass additions I will see one asset with two source lines but  I need to change the  cost of the asset before I post it , when I updated the