I need a workflow transition to test for a missing variable and a missing value.

I've created workflow to set the rev level of documents based on the revision table in the drawing. This checks for the revision property.

How do I process files that do not have a revision custom property or files where the property is blank?

I could put custom property in our template but files that come from other sources might not have it and would get stuck in the workflow.

I've created a macro that can check and set the properties but users don't always run it.