How to create a formula to subtract by part number and a value for 2 dates

[MikeFrancis1959]

I have a forecast that is from 2 different months and I am trying to figure out how the formula should be created. I have a forecast from March & May for 2 part numbers and a value for those 2 parts and I want to subtract the value based on part number and the month but not sure how to do it. I  want a formula to compare the part number for March to May and then get the delta between the values. I attached the small file and I show what expected results should be but I am looking on how I should create the formula, can someone please guide me as to what to do?

Thanks,

Mike 

[FinnCharlton · Accepted solution]

Hi @MikeFrancis1959 , here's one approach:

[MikeFrancis1959]

Thank you, this works and I appreciate the help! This helps me understand how to do this for other files I have!!!

Mike

[MikeFrancis1959]

I have a follow up question, I have parts that were in one month but not the other and the formula does not work. example: PN "A" has forecast of 500 in May and nothing in March so the formula does not pick up the 500 new pcs in May. I s there any way in Alteryx to compensate for this or just make sure the same part numbers are in both months ( can do this in Excel since this is a manual file put together before it goes into Tableau), any suggestions

Thanks,

Mike