InfoPath Dev

This Office Online post explains how to add a validation rule. Perhaps give this a try? https://support.office.com/en-us/article/Add-rules-for-validation-fa530b5c-419f-4c03-a85f-d7f96cb9de95

What's the rest of the code? What is the error you get?

So - if you create a new blank form, and add rules, you also can't copy / paste those? That is, this is not just limited to IP 2007 forms? I have occasionally had issues with rules pasting (same symptoms you describe) - but mainly it has been when I've got a few buttons with the same name, which confuses InfoPath....

Add a validation rule - if Admission Type = "Inpatient" and Room Number is blank, display an error to the user.

 Open the form library where the form is published in Windows Explorer. In the Forms folder in the library, you'll find template.xsn. Copy that out locally somewhere. Right click and select Design - does that open it in design mode? From there you should be able to resave locally, and republish when you have made your changes. EDITED TO ...

 Thanks for letting me know! I also updated the URL in my mention above in case someone doesn't read down all the way. :)

Great news, glad you have it working - and you got a chance to learn about REST. :)

Well, I think this part you don't need code for - I think you should be able to just use a calculated value in a table bound to your combined list - can you attach a copy of your form thus far to a reply under the Options tab?

I'm so sorry - I clearly didn't read your initial post well enough. The REST option that would let us get data from a related list relies on the list having a lookup so we can use $expand. Which is not what you have going on here! I really can't think of a non-code solution for what you want to do. Would it be an awful pain to add a ...

Awesome, glad you got it!