1) Are you sure there is a 'v5' in the data to begin with? Try using the same logic on other ones you know is there.
2) Make sure you are quoting the search term with single quotes eg. Field='Value'
3) What is your code for the text object? What is your end goal? If you are just trying to select 'v5' in a listbox, there is built in search functionality on the list box that you can customize as well.
I would however suggest you do flag this with numeric values in your data model. String manupilation is single threaded operations so if you expect large number of users it's vise to move the calculation into the script and just do sum(YourFlagField)