Avg function compared to Essbase avg function

[Hurdles]

I have an Avg formula in an Essbase member. I am trying to replicate this in MSAS.

Essbase formula
avg(expList)
expList can be any member that returns a number, whether the list is of members from the same dimension or not

myavg = avg(Jan:Mar,LA)

Jan:Mar is the set Jan,Feb,Mar from my Time dimension
TX is a member in my Location dimension
(it's sibling is LA)

Here are the numbers

Tx La
Jan 2 9
Feb 3 6
Mar 4 6
MyAvg 4 7

As a normal average for Jan:Mar for Texas it should be (2+3+4) / 3 = 3
but since I put in the (Jan:Mar,LA) the average is now
(2+3+4+7) / 4

Any ideas of how to do this in MSAS.

Thanks
Justin