jQuery Grid Plugin - jqGrid

hi, had a flick through the examples and the docs and just hoping am missing this, as it would be a 'nice' feature.  Basically what we have is a grid of data with adds / edits etc all working nicely, a lot of the columns are select boxes with values being populated on load (ASP function, querying DB, outputting json data).  These select box values are actually database table rows at end of the day, so adding a new select value requires a DB row to be inserted somewhere.  The scenario I have is as;

Go to Add / Edit record (appreciate the solution may be different for each), choose the column which is a select box and presented with values A,B,C,D  but we want to store 'E', so looking for a means of having a text input where they can type 'E' and it gets added (presumably with a background url query like the main form) and can then be chosen?

Asking too much, or just missing the obvious

TIA