VLOOKUP Performance Is Taking Very Long Time To Recalculate

I designed a spreadsheet which uses a lot of VLOOKUPs and it takes a very long time to recalculate. I don't know if there is another way I could do this, but this just seemed to make sense and it works just the way we want it but it just takes too long. Here is what the spreadsheet is designed to do:

We have data that is pasted into excel from another source. The data is broken up into account number, date, check number, and amount. Multiple payments from the same account can occur in one month so the data must be totaled. There is a custom function called concatif which works just like sum if but concatenates text. There are VLOOKUPs performed on the account number and the corresponding date, check number, and amount are inserted in the table.