Merge cells -find & higlight duplicates - add sum and then Delete remaining duplicate rows

I have attach a spread sheet with three tabs: I would like help to create a macro (will use marco daily on different worksheet with new download data) to do the following steps:

Merge cells =$B2&$C2&$D2&$A2 NOTE: B2= contract, C2=call, D2 = clin A2 = Inv

If any of the merge cells are duplicate then highlight

Add the sum all of the rows of QTY if the group match by contract+call+clin+Inv and then change the QTY on the first line to the total sum..

For example from attach worksheet)
Rows 21 thru 28 matches which I have found by merging $B2&$C2&$D2&$A2 and then highlighted duplicate if matches The next step: I added the QTY in columns E (QTY) rows 21 thru 28 which added to 17.
In row 21 I changed the QTY to the total sum of 17.

I would repeat this step with each merge match.

Sorry if I made this confusing, but I hoping my spreadsheet will help. I am open to a faster and easier way because some days I have 400 lines with 20 rows with same contract, call clin and Invoice but the QTY is different and I have to add and change manually.