To be fair using a combo is by far the easiest and most reliable method.
It has numerous advantages over a normal text box for this type of operation.
Firstly all the data you want is already there - as you are doing at the moment, simply retrieve the column values.
Secondly Users can't mis-type and enter something that doesn't exist, and if they do you have a selection of events you can use to handle that.
With a textbox, you would have to do the lookup or open a recordset to find the text, handle the fact it wasn't found, or do a load of other DLookups if it was found. (all of which is significantly slower).
What is steering you away from the combo ?