Jk-ford, you can probably do something as simple as running a resistor inline from the dome light to the relay, reducing the current enough so that you start just above the minimum pull-in voltage for the relay. This doesn't mean it won't chatter at all, but it'll go off very quickly and should click for less time, as you'll spend less time around the window.
I would suggest getting a 100 ohm potentiometer, and wiring it up between your dome circuit, and the relay coil. Tun on your interior lights, and then adjust down the pot to where any more change will cause it switch off (you may need to give it a little more space than this). Then use your multimeter to measure the resistance of the pot., use a resistor near this value, and replace the pot. with the resistor.
Otherwise, you can go by the pull-in voltage and calculate the resistor value from there, but a potentiometer will allow for easier adjustment.