switch between two voltage sources dependent on micro processor output

Ok so going with Les' method, if I were to connect it like this, and put a positive voltage to the gate then I would have the GND connected and so the dimming circuit would be on? Or am I misunderstanding the datasheet (https://www.fairchildsemi.com/datasheets/2N/2N7000.pdf)?

Hi SamV67,
Yes that is the correct way to connect the mosfet. It will be in dimmer mode when the gate voltage is at a logic high and at near the 24 volts when the gate is at a logic low.

Les.

Thank you so much for all the help