InfoPath Dev

I have a 40 character string inside a textbox where the 14, 15 and 16 characters must be numeric.

I am trying to get either on of these custom patterns to work -

xdUtil:Match(string(substring(., 14, 3)), "\d\d\d")
xdUtil:Match(string(substring(., 14, 3)), "\[0-9]\[0-9]\[0-9]") 

But, neither of these patterns seem to validate that the 14th and next two characters are digits.

The way I was firing an error on the textbox field was to set a second field with the value of Error in err situation and Good in situations where the text passed validation. And, in the first textbox I was messing around with different custom validation rules and having no luck getting them to work. So, I deleted the old rules and put in two new rules and viola, it all of a sudden worked with the following:

Good - xdUtil:Match(string(substring(., 14, 3)), "\d\d\d")
Error - not(xdUtil:Match(string(substring(., 14, 3)), "\d\d\d"))