Displaying Values in Proxy Field

Hi Don,  thanks for replying.  I tried option two.  I think it is working, but my issue with that solution is you cannot (atleast in the way I have it setup) select the Brand from the formula Text field.  You still need the Original Proxy field to make the actual Brand Selection.  Is there a way to do this with just one field?  

My issue with option 1 is when the user is making the selection both fields mimick each other.  It is not until the form is saved that the "Percent" field changes to the appropriate % associated to the selected Brand.  The goal is make certain the user is selecting the proper Brand and Percent as there are Brand names that have 3% or 5% associated to it.  The below screen grab is the form in edit mode selecting the Brand "Comet 3%".  You can see the % field displays the brand in edit mode.  

Here is the form after Save.