Temporary Variable in Infopath Form

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InfoPath

SharePoint2010

Hello,

I am new to Infopath and i am using this in Infopath 2010.
I have a requirement where the sharepoint list is getting updated on Submitting the infopath form after checking a condition.
The condition involves 2 AND operations which looks like this
If (a!=b) && (a=='Some Value') then counter++,
over here i need to set the value of B on the page load and then do the check.
This is pretty much like the selected index change in asp.net dropdownlist.
But how will i implement it over here is the question.
Any help is greatly appreciated.

Thanks