jQuery Grid Plugin - jqGrid

I need to populate one of the search fields with a list of usernames (with the key/option value being the user id). I can do static select lists in the jqgrid colmodel setting using stype:select e.c.t. However, is there a way to modify this select list after the grid has loaded.

I have the events i need, and i have got to a point where i have a js object of id:name pairs ready to inject into that select list in the search popup, just need the last little bit (or just the function to use, so i can look it up in the wiki).

Any help would be appreciated 🙂