Sumif and if formulas

Good day I've attached a file as reference

I'm looking for a formula to that will do the following please;

The formula must be on sheet: (Summary) column: C9 to C17 (Opening Balance) and J9 to J17 ( Balance to Syspro)
This is what I want the formula to do; if you go to sheet: (Month) the financial year:I2 is 2019 & the financial month:H2 is period 3. Then the formula must be the sumif from sheet: (StockBalance) column J:J (OpenBalQty1) per warehouse as my opening stock quantity and sumif column E:E under (StockBalance) as my closing stock.

And if the Period on sheet: (Summary) D5 is one less than the current financial month which is period 3 under sheet: (Month) H2. Then my opening stock under sheet(StockBalance) must be the sum per warehouse of column:K:K and my closing stock must be column:J:J. And if the Period on sheet: (Summary) D5 is two less than the current financial month then my opening stock under sheet(StockBalance) must be the sum of column:L:L and my closing stock must be the sum of column:K:K per warehouse. The sequence must be the same going backwards to the previous financial year that would be period 12 of financial year 2018 then opening stock will be the sum of column:M:M and my closing balance should be column:L:L under sheet: (StockBalance) and so on.


I hope I'm making sense

See if this will get you started?
C9=SUMIFS(StockBalance!L:L,StockBalance!$D:$D,Summary!$A9)
copied down.

That will give you the basis for all the other calcs you need to do. If not, shout back and I will assist further