ICSP and 3V

Hi,
I'm making a project where I'm using a microcontroller operated by a 3V coin cell (it's very low power consumption), it's also powering a 3v ONLY module.
I included an ICSP header to program, but i realized if i power it with 5V while programming it, the module will be damaged
I was thinking about adding some diode somewhere to protect it, but I'm not sure if it's good practice.
Anyone have a recommended solution?

I don't know what processor family you are using, but many of the Microchip parts can be programmed at 3V. You do need to change the default voltage in the Pickit, but that's easy to do.

One thing to watch for though is the erase voltage. I was using a PIC10F220 on a coin cell powered project. It would program ok at 3 volts. Once. But I could not reprogram it to try new code. Turns out that the erase voltage needed to be higher. Luckily I had the coin cell in a socket so I could remove it when I needed to update the code.

If you go into the programer menu and select properties you can select the voltage to power the pic, of course as chris just said the pic needs to be able to run at that voltage, but I spose you allready know that it does using a 3v battery.
Mplab gives you plenty of warnings if you change the voltage.