Custom Field Integrity Checking

[Rogue_SSEi]

We are requiring names during registration. I have created a first and last name custom field and set it to required and this works well. What I would like to do is check the Last name and first name fields to see if they contain more then 1 letter as we dont want Initials or incomplete last names.

I'm assuming I would do this with a reg expression check but unfortunately I'm not good with reg expressions.

Can anyone help me with this or advise another way to do the check?

Specifically looking for a way to check the field and if it only contains 1 letter then prompt them to fill in a complete name.

Thanks