GENERATE A NEW JOB/PROJECT NUMBER WHEN YOU OPEN A SPREADSHEET

Dazzaman35901968 

See if this does what you want:

Press Alt+F11 to activate the Visual Basic Editor.

Double-click ThisWorkbook in the Project Explorer pane on the left hand side.

Copy the following code into the module:

Private Sub Workbook_Open()
    With Worksheets(1).Range("B1")
        .Value = .Value + 1
    End With
End Sub

This version places the job number in cell B1 on the first sheet. You can change that in the code if you wish.

Switch back to Excel.

Save the workbook as a macro-enabled workbook (.xlsm).

Make sure that you allow macros when you open it.

See the attached sample workbook.