jQuery Grid Plugin - jqGrid

What I'm attempting to do is have a primary grid that contains two columns - ID, Description. When adding/editing one of the rows I would like to have a second grid represent the "ID" field allowing the user to search for a specific ID already predefined in another location. The description field would be a normal edit field.

If this isn't directly an option is it possible to add a button in the add/edit form to display a second grid in modal form and then on selecting a row in that grid pass the selected "ID" back to the edit form?

Any suggestions / recommendations would be greatly appreciated.

Thanks