Data Source / HTTP Test Request Sequence - How To Loop?

I am a SoapUI / LoadUI rookie, so I apologize if this is a trivial question. FYI, I am using a licensed copy of SoapUI Pro 4.5.1, but I am not the registered user (my manager is, and she doesn't have the software installed on her machine), so I am posting this question here.

I am trying to create the following test case:

Loop through the following sequence of test steps:
1. Excel DataSource #1
2. HTTP Test Request #1 - Using parameters from reading a row of data from Excel DataSource #1
3. Excel DataSource #2
4. HTTP Test Request #2 - Using parameters from reading a row of data from Excel DataSource #2

For each iteration of the loop, HTTP Test Request #1 should read the next row from Excel DataSource #1, and HTTP Test Request #2 should read the next row from Excel DataSource #2.

The sequence should execute indefinitely (until I stop it). If Excel DataSource #1 runs out of data, then it should cycle back to the first row. If Excel DataSource #2 runs out of data, then it should cycle back to the first row. (The two Excel files might have different numbers of rows.)

I experimented with DataSource Loops, but they seem to work only with a single data source test step and a single target test step.

Thanks in advance!