editing data grid column via scrip

[Hershel F]

Hi everyone, i searched high and low for this without success.
Question, i have a data grid (trying to to set up an invoice form),
columns, costumer_id, product_id, company_name, product_name, price. etc.
option menus in product name and company name, 
Now when i use the options to select a product name, (product_name col.) i want to put the product id  into the product_id column by selecting the option menu btn, i tried many ways even when it went in it didn’t show up in the send "printkeys" to group  “data_grid_0” . all help would appreciate it.

Thanks in advanced. Hershel F