InfoPath Dev

I have a Repeating Section that contains 5 repeating tables, 2 of which are optional. I am trying to create an expression that can correctly add together fields from the footers of each table, but it only seems to work when all of the tables have data. When I do not put data into the optional tables then my grand total formula just gives me 1#QNAN. How can I create a formula that correctly handles these optional fields?
TIA
Dean

Try this:

Tools -> Form Options -> Treat blank values as zero

Thanks, but I already have that option checked. Any other ideas?

Sorry to insult your intelligence, Dean. :)

This is a rather interesting problem, and I think I have solved it with this formula:

concat("0", field1) + concat("0", field2)

The problem was that the node wasn't blank, it just wasn't present. So, tacking a zero to the most significant digit will allow the nodes that are not present to simply be a 0 in the equation. I hope this helps!

Matt, this works great when the values in the Optional sections are greater than 0 but fails when they are negative. Any idea how to modify this to work when field1 and/or field2 is less than 0?