Lookup field filtering

Lookup field filtering

Hello,

I have a lookup field that I need to filter based on input in another field. I have already filtered this by setting the filter in form builder to Model(look up field) contains input.Model(single line text field) and this filters it almost the way I would like it to except for a small problem. For an example I have a models in the look up field that are called 49 and 49F so the problem is when the input  49 into the single line text field it includes the 49F in the drop down of the look up field because I am using contains. The reason I am using contains is because when I enter 49 into the text field I would like all modesl that contain 49 to show up. So for example I want a 49-LD to show up and 49-HC-LD but I do not want a 49F to show up. So basically  I would like all the models that contain 49 and don't have an F to populate the lookup. I hope that makes sense and if you have an idea on how to approach it would be greatly appreciated.