The short, accurate answer is to buy Ben's kit @ poolsolutions.

A stop-gap method that is not very accurate is to dilute your cl test water by adding 4 parts distilled to your pool water, then multiply results by five (or dilute 3:1 and multiply by 4, etc). This method, while cheap, is very inaccurate but may get you in the ball park if you do it carefully and dose carefully.