InfoPath Dev

I am using an eval function to populate a text field from repeating table rows -

eval(eval(EmployeeNextels[EmployeeRadio = "Yes"], 'concat(my:EmployeeNextel, ", ")'), "..")

This formula is the default value of the text box being populated.

Is it possible to combine eval functions so that it gets it's value from two seperate repeating tables?

Yes. Assuming both repeating tables have field EmployeeNextel:

eval(eval((EmployeeNextels1[EmployeeRadio = "Yes"]|EmployeeNextels2[EmployeeRadio = "Yes"]), 'concat(my:EmployeeNextel, ", ")'), "..")

What if they don't both contain the field "EmployeeNextel"?  The second one has a field called "StaffNextel" instead.

Just concat them together. If the field does not exist its value will be an empty string:

eval(eval((EmployeeNextels1[EmployeeRadio = "Yes"]|EmployeeNextels2[EmployeeRadio = "Yes"]), 'concat(my:EmployeeNextel,my:TotallyDifferentField, ", ")'), "..")

Perfect.  Oh, man, thank you very much!!!!!