Help with Excel

[cool_coolioin]

I searched the entire forum and couldn't get a good answer. I have created an application which stores the information in an Excel file.
I have created the Excel object inside a form. On the click of a command button an excel file is created and the data is saved. There seems to be no problem if two or more excel file is created. But when I reload that form again and try to create excel file. It gives "_Global failed". The excel application quits only when the program is closed
The code is

Dim xls As Object

Private Sub cmd_Make_Click()
xls.Workbooks.Add
xls.Workbooks(1).Activate

' Code to write to the Excel sheet
Worksheets("Sheet1").Cells(1, 1).Value = "Sl. No"

ActiveWorkbook.SaveAs App.Path & "\Excel\" & strFileName, xlExcel9795
xls.ActiveWorkbook.Close
End Sub


Private Sub Form_Unload(Cancel As Integer)
xls.Quit
Set xls = Nothing
End Sub