Aha! Do a search within PoolForum for the Shot Glass method! You'll need a bottle of steam distilled water, which your local grocery or discount drug store has.

The idea is you dilute pool water and then measure the chlorine in it. So...if your kit goes to 5 (and I assume it's an OTO kit with yellow reagent), then if you mix a shot glass of pool water with a shot glass of distilled water, when you measure it, when it reads "5" on the tester it's actually 10ppm! Mix 2 shots of distilled to one of pool and it as if the scale goes to 15ppm!

Got it?