combination of a Vlookup and If formula

Hi team

I am having trouble writing a formula. The way I have tried to approach my problem is using a vlookup and =if but I cant quite get there. What I have is a master sheet with Part A, Part B and a Part C, each of these Parts have there own sheet. I wanting to grab the data from each of their sheets and bring it back to the master sheet. In the master sheet I have a formula in G1 to bring back the current month. I then want to use a formula to match that month against the month in the corresponding part sheet and bring me back their number. I have attached the sheet. I want the formula to bring back the numbers that are in E4 to E6. Bonus points if you can get the previous months numbers but will be happy just to get current


Thanks for any help!
Test.xlsx