Compare Sheet 1 and Sheet 2, and find matches and non-matches

I have 2 excel sheets in a workbook. Sheet1 and Sheet2. There are four columns of data in each sheet A,B,C and D. The code have to do the following:

First, Copy Sheet1 into a new worksheet.(e.g. Sheet3)
to copy the sheet right-click on the worksheet tab and select copy. when the dialog box comes up remember to tick "make a copy"

Next, program will run Sheet3 column A and match against Sheet2 Column A.
For data that matches, Sheet3's Column E will be updated with Sheet2's Column D.
formula for sheet3 column E, assuming there are values in Column E already:
Then in a blank column
=if(Sheet3!A1=Sheet2!A1,Sheet2!D1,Sheet3!E1)

Then copy the column and "Paste Special...Values into column E


Then, Sheet3's column F will be inserted with a formula to (C-D)
=C1-D1

Lastly, whatever that is not matched in Sheet2 and Sheet3 will be compiled in Sheet4.
I lost interest in trying to work out what you mean here