Populate field in background on OTL Timecard

Hi all,

I've been tasked with modifying an OTL Timecard Layout on EBS R12.1.3

I'm using the "Projects-Purchasing Timecard Layout" as basis.

This layout has Purchase Order Number and Purchase Order Line fields for each timecard entry line. We are using this type of timecard for IP's and as the Purchase Order number and Line are set against each IP's assignment, there will always be only one value for each field.

My requirement is therefore to hide the Purchase Order Number and PO Line fields, and yet still populate these fields with the single value available in the LOV for each line - essentially I want the LOV to fire in the background if this is possible.