InfoPath Dev

How do I make controls required only if a radio button a control is a certain value?  I know I can do this based on the OnAfterChange, just not sure what the code would be.

Just to rephrase -

 Is there a programatic way (Vbscript) to set the attribute (Can Not Be Blank) for a control?

example:

if (XDocument.DOM.selectSingleNode("//my:err_user_catagory").text = "False") then XDocument.DOM.selectSingleNode("//my:NumberUsers")..... (set this field to Can Not Be Blank)

use data validations for that

suppose u have two fields

field1

field2

field2 is required only if field one has "yes" value.

on field2 rightclick and click data validation -> Add

field1 is equal to Yes  and

field2 is blank

then enter the tip .. and click ok

now this field will be required if field1 = Yes