InfoPath Dev

Currently we have this need, we would like to add up the Nth row of a Repeating Table of EACH instance of one Form, and use it as the Nth row of a Repeating table inside another Form, could we accomplish this without coding? or worst case using XPath? To help illustrate what we want let assume each row only has one column:

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Form1(FORMA Template)  -> RptTable001  ->Row1: Value 11; Row2: Value21

Form2(FORMA Template)  -> RptTable001  ->Row1: Value 12; Row2: Value22

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Form3(FORMB Template)  -> RptTable002  ->Row1: Value 11+Value 12; Row2: Value21+Value22

Thanks 

Hmm, now I remember "SharePoint is a flat data structure and does not support repeating elements with a row", in the promoted field for that column of Repeating table, the value would be Value11&Value21 and Value12&Value22 already...Feels like we need to deliminate them in some way and then break them apart before sum them up....pretty tough chore.