Put the detergent tablet in the bottom of the dishwasher, never in the door compartment.
What's your motivation for this?
Wouldn't this just make the detergent get used up in the first cycle, which is usually the shorter one iirc?
Also, why the recommendation for using a tablet over powder? You get finer control over the dosage with powder, it's a lot cheaper, and you can actually fill both the compartments of the detergent compartment, meaning that you get detergent in both the rinse cycle and the wash cycle, for maximum washing efficiency.