The company I'm working for is looking to hire a senior developer with more experience than me, and they expect me to do the technical part of the interview. I've only been programming a few years and am not sure I have the knowledge needed to evaluate the coding skills of someone who has greater understanding/experience than I do.

Can anyone recommend some technical interview questions to ask that are a good means for evaluating higher-level programming skills, but still be ones I can understand? 

I would say I'm past the jr. programmer level, but nowhere near senior. Most of what I've done is built small apps (web and desktop), some of them fairly complicated, but all of them have been meant to be used by no more then a handful of users. I feel I have a decent understanding of most programming concepts and am capable of learning/teaching myself just about anything, however I lack experience. As my boss is fond of telling me, "You don't know what you don't know".

In particular, things we'd like the person we hire to have experience with (that I don't have) is: Multi-tier development, multi-user environment, large-scale application development, two-way messaging, shared sessions, and Multi-threading/BackgroundWorkers.

UPDATE: 

In response to Thor's comment below, we hired someone a few months ago and I think it has been working out great. I am learning a lot, not just about coding but also about things like design patterns, software architecture, documentation, and how other larger programming teams get stuff done. Its not always easy having someone come in and point out better ways to do things you have done, but if you can swallow your pride and be willing to try out new things you can learn a lot.

The interview process went better than I expected. I started asking questions about things I was familiar with, then asked some questions about some things I was struggling with. Whenever the interviewee said something I didn't understand, I'd ask them to explain it to me and then write it down so I could look it up later on. Overall, I felt I was able to get a pretty good idea of the applicant's skill level, intelligence, and what they'd be like to work with.

You can't.

Instead, I would suggest you to come up in the interview with a list of problems you have today, and ask him how he would solve them.

This a is very interesting method for the following two reasons:


It is free consultancy. Even if you don't hire the guy, he may suggest nice solutions to your problems.
If he comes with interesting solutions, he is a problem solver. The kind of guy you want to hire.

