The best way to attack this common problem is through the boss for whom you are Executive Assistant, I think. (Perhaps the he/she is the president of the company?) The problem isn't really that you're running around finding staplers for people. It's that you're paid to perform a higher-level job, and still finding staplers.

So you need to track your time for about a week or so, and the kinds of requests that you get. Consolidate it into an outlined list--I imagine this is second nature to you. And then have a conversation with your manager about what you should be spending your time on. This should be easy for you, I think.

The harder problem that you might have is saying, "No," to some of the requests that you get. After all, a good office manager never takes no for an answer. Consider it an aspect of professional and personal development. (Try it out on your husband...). Once you get clear on your role, I believe that it will be easier to say no: after all, you'd just be doing your job.