Karen,
I would figure the points for the marinade and measure it's volume. Use the marinade, then measure the left overs. You should be able to easily figure how many points of marinade is sticking to the chicken, then divide that number by the number of pieces of chicken. It's likely it won't substantially raise the point value of each piece of chicken, but to be safe I would do this once to be sure. It just depends on how stringent you are on keeping up with your points!
Enjoy the tandoori, and if it's point-friendly, post the recipe so we can all try it out!
Annie
290/214/150