First you need to make the button a rules type by changing the drop down in properties. Also I believe if you add a button it is a rules type by default.
Then you can add a rule called Submit.
And add an action which is a submit to data connection and pick the first data connection you want.
Then add a second action which is a submit to data connection and pick the second.
Then you can get all fancy and add lots more actions or conditions, etc.