Loading unlimited User and Node references

I'm working on a rule that will allow me to add multiple referenced users to multiple referenced nodes. The rule I have can successfully add the first user to the first group but the extra users are ignored.

Currently, my rule checks for the content type and, if it's the correct type, it then loads the node reference and the user reference and inserts the specified user into the specified node. Any ideas on how I can extend user and node reference rules to load multiple values?