how to have a cell copy another cells data base on other criteria

I have entered a formula in Tab AG ORDERS in column L which is working but I want to adjust it so if column a is blank then it looks in column d and if the data in d matches, then it enters in the same info in column l.

SO example A22 - A29

I have data in A22, so the current formula in column L enters in data. I don't have data in A23 - A29 but the data in D23 - D29 all match, so I want the data that was entered in L22 to replicate in L23 - L29

Is this even possible.14-15 budget-AG test.xlsm

L22 has the working formula that I want to add to

That didn't work, if the cell is blank it is pulling the data in from the cell above which isn't always the cell it needs to match. any other suggestions?

Obviously the formula needs to initially start with my formula =IFERROR(INDEX('Reference List'!$C$2:$C$22,MATCH(A22,'Reference List'!$D$2:$D$22,0)),"")). But maybe there is a way to write it differently. If A is blank then if match D to the row with the same info in D and has "SPO" in column B and enter whats in L.

So if A2 isn't blank and has SPO written in B2 and has 1234 as the PO# in D2, then every row that is blank in column A but has the same PO# in column D enters the same data from L2 in their L cell. Any suggestions? I realized there is data validations on D,E, and F which are wrong. So please disregard those.