InfoPath Dev

I am developing an InfoPath 2007 form. I want to clip the content of Rich text box to specific character limit e.g. upto 400 characters if exceeds than that. I want to sustain the markup generated. Can anybody suggest me the steps to be followed. Thanks in advance :)

I tried it but it does not restrict user to type the content beyond limit. BTW I think I am very near to the resolution.

I am developing an Infopath which contains richtextbox. I have set some data validations rules on that. I want the user to be restricted to put the text beyond perticular character limit. I have tried to do it through conditional formatting but could not achieve. I even tried to achieve it through _OnAfterChange event of the ...