Add worksheet in an existing workbook

First of all, you're mixing methods.

Use Early Binding to improve the speed of your app drastically:

First, in VB, set a reference to the Excel Object library. This done, you don't need the call to CreateObject.

Then try this code:

Public ExlObj As Excel.Application
Public Exlsheet As Excel.Worksheet

Set ExlObj = New Excel.Application
ExlObj.Visible = True
ExlObj.Workbooks.Open ("c:\myfile")

Set Exlsheet = Sheets.Add(After:=Worksheets(Worksheets.Count))

' You could save the file with:
ExlObj.ActiveWorkbook.Save

'And DON'T forget this line when you're all done:
ExlObj.Quit 'closes Excel completely

That will do what you want.

-Andrew