Throw these lines at the end of the function away:
VB Code:
  1. 'Now we re-call the function to find the next occurrence of the string
  2.     FindIt = 1 + FindIt(Box, Srch, Start)
Then you are all set....

But there is a little extra programming to do first!
You need the variable Start to be globally available (DIM it at the top of your program, or in a code module), so that you can call FindIt with the Start parameter each time the user clicks on "Find Next".

Make sure you know what the user wants when clicking on "Find". Do they mean: start where I have got to and look further. Or do they mean: start at the beginning and look from the beginning.

You may well need a Find and a Find Next button. The FindNext button should [probably] only be visible after the Find button has been clicked. Should it also be available when the user has got to the end of the FindNext loop?