InfoPath Dev

I would like to see if a database field contains some string value then show one filed and if not show another field. I tried to do this in the rules by using "Contains" function in the form load rules, but it appears that I don't know the syntax of the rule writing very well, so can somebody show me the syntax, if it is possible to do so. Somethign like this, but with correct syntax:

LoggedInAccount = (userName(), substring-after(userName(), "\")  contains(userName(), "\")

Using an XPath expression to select between two or more values can usually get a bit messy.  In this case, this should work:

substring(userName(), string-length(substring-before(userName(), "\")) + 2 * contains(userName(), "\"), 100)