It is possible in some cases. You should go to someone who knows what they're doing, typically not HD, but more like a local paint store that sells to contractors. I don't know where you live so can't make a specific recommendation. You will typically need a pretty good sized chip, square inch or so.

Michele,
Realize also that even if the color is DEAD-on, just the newness of your touch-up will be noticeable at some angles.
* Get a flat sample like Pilam said. Tape it to a piece of cardboard for easier scanning.
* Note also what sheen-level your existing wall is...flatter or shinier.
* Do you need a gallon or quart? If it's a real light color, a gallon might be your only choice. Some formulas are so small they can't be shaved down into a quart.

Good luck,
Faron

Thanks, I'll give it a try. Keep my fingers crossed!!!