Creating MEDIANIF and MEDIANIFS in Numbers '09

Does anyone know how to create a MEDIANIF or MEDIANIFS similar to the available functions AVERAGEIF or AVERAGEIFS.

I would like to take the median price of homes built on or after 1970, but there is no function: MEDIANIFS(SOLDPRICE, Year,">=1970") like there is for AVERAGEIFS.

Thanks--