Trying to change keyframe to be affected by source text

Hi All, 

I am trying to make template. I want it so that all I have to do, is enter in a number in a text field and then the number will change automatically. I have a key frame at 0 and then another keyframe at 85. This makes it so it looks like its counting up the numbers to 85. I found the eval expression but how would I make it so that I can keep the first keyframe at 0 and then have the second keyframe depenedant on what I put in a text field?