What a brilliant idea. As I see it, each node/element would require an ID or node-number (it probably has this already, though hidden). This should be revealed in the Data section. Also, in the Data section there should be a 'Value' field, which looks like a spreadsheet cell, and contains a value or a calculation, and a format. The General->Text field should be able to reference any node's Value field (including its own), using a spreadsheet-like reference. For example, say, node 125 has in its Value field: SUM(#101,#103,#107) - and in its Text field: "Given #101, #103 and #107, the total is #125". Hidden (non-visible) nodes could be used for intermediate calculations. I got some ideas from a similar implementation in Javascript - see jazzyforms-dot-com
