InfoPath Dev

I have sections on a form that should be signed.  I have the digital signatures setup and working with no issues.  However, I need to do some conditional formatting based on whether or not the section has been signed.  How do I go about setting up the conditional formatting on say a button or a textbox?

Form details: web-based, Infopath 2007

Thanks!

Double click on the textbox. Go to Display tab. Click Conditional Formatting. Click Add. In first dropdown select "Select set of signable data" and add the section that you have a digital signature on. In second dropdown choose "is signed".

What does it mean when I don't have "Select set of signable data" in the first dropdown?  The options are a few fields that I have on the view, expression, and Select a field or group...