How do I turn a pump on based on one temp being x degrees higher than another ?

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I need to make mango turn a pump on when 1 temp sensor is x degrees higher than a second temp sensor (all 1 wire devices)
Any clues on the best way of doing this.

Thanks

1. Create a meta point that calculates the difference between the two points
2. Add a high limit detector on to the meta point
3. Add an event handler to the high limit detector that turns on your pump.