XF 2.2 Custom field validation?

[cdub]

If I have a custom field and the first couple of letters and numbers will always be the same if they enter it correctly... is there a way to make sure that that's what they enter?

For example make sure whatever they enter begins with the letters "RN" ?

 

[Paul B]

This should work:



You can modify the content in the square brackets, depending on what other characters are required - e.g. only numbers, or letters.