[ASO MDX member formula] Trying to use AVG depending on PTD/QTD/YTD

Summary:

Working with an ASO cube, I am trying to develop a member formula to calculate the average of another stored Account across the appropriate periods

My goal is as follows:

If PTD, make it equal to AC_Finance FTE

If QTD or YTD, calculate the average of AC_Finance FTE across the periods to date (for example, April through May if pulling QTD May or Jan through May if pulling YTD May)

I am very new to MDX, but I am struggling with following the documentation on this. I thought I had set this up correctly for QTD, but I cannot seem to specify AC_Finance FTE in the second THEN. Any help or guidance would be greatly appreciated!