Allam,
Your question is a but vague. If the user types abc into a textbox that has an inputmask of Replicate('X',30) then the length will be 30 or 3 depending how you check it.
lnLen = LEN(TRIM(Thisform.Text1.Value))
lnLen = LEN(Thisform.Text1.Value)
I used trim so that if the user enters " abc" the typed in spaces are counted.
What value doid you want to see as a result?