How do I know which sheets are to the RIGHT and LEFT to the Active Sheet?

Hi e4excel,
You are asking to different questions.
If you have different "Workbooks" then these are different files on your harddrive or server.
If you have different "Worksheets" then these are different tabs in a single workbook file.

You have mixed these words in your question above.

If you meant different TABS on a single WORKBOOK then you can use an index number to address the different Tabs or Worksheets.

Worksheets(1) would be the first tab, on the very left of a workbook
Worksheets(Worksheets.Count) would be the last tab, on the very right of the workbook.

hope this helps.

To answer the thread title is this. Your current worksheet number is "Activesheet.Index". So to access the sheet to the left is Worksheets(Activesheet.Indes - 1). And + 1 to get the worksheet to the right.