If no match exists create a match

[melfinance]

I have four column of data. The first two columns are data from the prior month, say January. The first column is an account number and the second column is an invoice number in the account. The other two columns of data are the same data format but with data from the next month.
What I am trying to do is to get each account and invoice to line up next to its match from the previous month. The tricky part is sometimes either an invoice no longer exists in an account or an invoice is added.
What I need is for excel to compare the two lists and to say okay I checked the list and this account no longer has this invoice so I am going to copy the previous months and put it into this months data. Or this account was added I am going to insert a line accross from the new account and add it to the previous months data.
They all have to line up directly accross from each other in the spreadsheet.
I think what I need is a giant if statement that has a lookup based on two criteria. Tricky

 

[just_jon]

I think a small sample with expected results might help?

 

[melfinance]

Here is what my sheet looks like before I cut and paste all the rows to line up next to each other. I have to see if both MGMT and Invoice are the same. If they are the line up next to each other. If not I have to add a line with the missing or new invoice number in the MGMT code.

 

[just_jon]

Board functionality's a bit off at the moment; if you'd like to email a sample of your data, as well as expected results, let me know.