InfoPath Dev

I want to set multiple values in a lookup based on information entered earlier in the form. I've been round and round the internet reading articles and not getting anywhere. I can get all the individual ID values out of filters and other rules, but I can't seem to write the values into the muliple value lookup. Whatever I try I only ever seem to be able to write the first value into the lookup. Is it possible with an Infopath 'set field's value' rule, or am I wasting my time?

It isn't possible, and here's why. The data structure for a multi-select is repeating. InfoPath includes one blank instance by default - when you select or deselect items in your multi-select, nodes are added or removed. If you preview your form and select a few options, then use File > Save As to save the file, you can open the XML in a text editor, look for the field bound to the multi-select and see what I mean. InfoPath has no built in way to use rules to add (or delete) instances of a repeating node.

Thanks Hilary. I wish I signed up to the forum earlier - you'd have saved me hours of googling. I had come to that conclusion, and am now trying to write the values into another field to then utilise in Nintex instead (hopefully), as I've managed to do something similiar with Nintex for loops before. Really appreciate having this confirmed and the clarity on why.