InfoPath Dev

Hi guys

I want a field that calculates the difference between 2 dates (date pickers).

The following link details a lengthy way of getting this:

http://www.bizsupportonline.net/infopath2007/calculate-date-difference-infopath-rules-formulas.htm

But I only want to calculate working days. Anyone know a way of achieving this? Thanks :)

 Have you seen this? https://alecpojidaev.wordpress.com/2008/12/30/infopath-codeless-programming-walkthrough-2/ 

There are some sample forms that apparently do this. :)