In many places I have worked, one's programming skill was measured (by non-programmers) simply by how quickly and how often you say "no". Their thought process went something like this:

You clearly are not a good programmer because if you were, you could do what I am asking you to do.

And no, it did not matter if what they were asking you to defy the Laws of Math/Nature/Physics/etc.

Over time though I found the antidote to stupidity such as this is to say "yes", then explain to them (in great depth) the many ridiculous steps you would have to take to accomplish it. And then if they are a paying client, tell them how much it will cost them. If delivered calmly and clearly without sarcasm or bitterness (always best to keep those things to yourself) this would usually result in you looking good, and not having to accomplish said ridiculous request.

Of course it does backfire sometimes, but then you just look at it as a challange ;-)