Ok, I think I am starting to understand better now. The IF field code(and any embedded field codes within the IF) is converted, but other field codes are not. So if I had a field code which had an embedded IF field code, The IF would be converted, but the parent field code would still be editable?

Wherever I would use an 'IF [condition]', I can convert it to a formula as you have posted for mail merge? Does this work in a normal document that isn't being used for a mail merge?