SSAS 2008 MDX Calculate Average Between Two Measures

Hi,

I need to be able to calculate an Average over two seperate measures within a SSAS 2008 Cube.

In my cube, I have two measures, one called [Measures].[Order Quantity] and the other called [Measures].[Order Quantity Week On Week]. The later is a Calculated Measure.

I need to be able to find the Median Average between the two.

So, if [Measures].[Order Quantity] = 1000 and [Measures].[Order Quantity Week On Week] = 1200, I need the Calculation to return 1100.

Is it possible at all to Calulcate an Average over two measures in MDX ?

Thanks