Is it Possible to Change Invoice Group Flexfield to a List of Values text box on Invoice Header?

Summary

There is an Invoice Group text box on the Create Invoice Header. I'm trying to find out if I can link this to an LOV to stop miskeys by users.

Content

I'd like to be able to create a List of Values for the field "Invoice Group". "Invoice Group" is a text box that is on the Invoice Header. I don't seem to be able to have the same options to change this as I do with DFF's. I'm not sure if that is b/c it is a seeded flexfield or I'm looking in the wrong spots.

The goal is to lock it down to a list of about 5 values that the user would need to pick from. Right now it could be anything they type in when they create an invoice.