Hi Usman,

In the Administration Console, go to your repository's fields node and double-click the field which you want to apply the constraint to.

In the constraints box, you can try entering the following regular expression:

[A-Z\s0-9]+

This regular expression allows characters between A to Z, a space and between 0 to 9.

If you press the "Constraints..." button, you can also configure the error message users will see when they enter lower case letters.

Link to Laserfiche Help Files Regular Expressions