How about starting with... "can I ask you a question?" then ask the actual question. What if I say NO to question #1?

If you need my attention, and have a question, how about starting with Excuse Me, where/what/how .....?

I have been known to answer Can I ask you a question?, with No. Then ask why do you use that leading phrase? Just ask the question! (and the voice in my head is phasing it a bit differently and less polite. Bad voice bad bad voice).