Returning multiple values using IF statement or IF ELSE

Thank you for a great resource. I looked for a similar question and failed to find one.

I need to report prior Quarter to Date data. I have inserted RANK into the [Month] data to use as a distinct number that can be used in variables. I now need to write a formula for a variable that will be used to pull the months in the prior QTD.

Here is what I am up to (I'm open to a new approach):

IF([Count Current Quarter] = 1, then 6        (returns the first month of prior quarter)

IF([Count Current Quarter] = 2 then 6,5      (returns first two months of prior quarter)

IF([Count Current Quarter] = 3 then 6,5,4

I tried using an IN statement but failed.

Thanks for letting me use your brains!

Bob