How can I make a textbox to accept a text with a specific structure and length to activate a button?

In a section of the game, the user has to write in a textbox something, with the following structure:

mon_2ft4up

10 characters in total (3 letters + underscore + 6 characters)

Only written that way, a button will be enabled.

I will appreciate your help.

It worked!!

dop2000 I followed your script and it's exactly what I needed. Thank you very much

In addition I started to investigate according to your advice on len () and I found how to put a maximum of characters, in case someone needs it, this is the result.

System Compare two values RegexSearch(TextBox.Text, "[a-zA-Z]{3}_[a-zA-Z0-9]{6}","g")=0 -> Button set enabled

maximum number of characters: 6

System Compare two values len(TextBox.Text)>=7 -> TextBox set text left(TextBox.Text, 6)