Regarding Form Personalization in AR Tranasactions

Hi,

There is a button on Transactions Screen "Complete".

I Have to keep it disabled for certain Sources like "Project Invoices" defined as a source in the system.
I want to do it through Form Personalization.

But I am unable to decide on to what event should i get this check fired

also, I am unable to get what is the name of the button in the system...so as to reference as

Button.disabled='False'

when i used the "TGW_HEADER.COMPLETE_FLAG".disabled='False'

it disabled the check box for complete flag

Please help to resolve it ASAP.