Pop Up vs Combo for links.

I am trying out the use of Combo box for 'Show Field As' rather than Pop Up.  I like the Combo Box option but it seems that there is no way of circumventing the field choices (when using Pop Up) displaying in the linked field once chosen.  Show Data As is set to only show the Model Number but because the field shown when using Pop Up method includes  2 other fields they too get included in the field even when using Combo Box.  Boy I hope that makes sense.

I have the Model No, Description and Thumbnail in the 'Pop Up' method to assist selection but I only want to see the Model Number in the field once selected using Combo Box.  The Thumbnail and Description are displayed in formula fields once selected.

Here you can see the description tagged on to the end of the Select Model Number Field.
Is there anyway I can have the description and thumbnail dispayed when selecting but only show SWYTCH BYOD (in this case) in the Select Model Number field?
 

Thank you