I need help with setting up validation for a field.

I was asked to do the following.

If a checkbox has been check, check to see if a comments field has a value.  If it doesn't, we need to display a popup to the user.

Here is my expression

([<bNo_ITAG>]='N' ) OR ([<bNo_ITAG>]='Y' AND [<ltComment_ITAG>]  IS NOT NULL)

This is for Lead Management and Quotation Approval.

EDIT:  I updated my expression, but I'm still having issues