I'd solve my problem now!! hope this may help other..

1. I change type of variable oExcelApp from Excel.Application to Object and same for workbook & worksheet
2. You must be sure ,u have Excel'd installed on ur machine.

VB Code:
  1. Dim oExcelapp As Object, oExcelwk As Object

  2.  
  3. Private Sub Form_Load()

  4.  
  5.     On Error Resume Next

  6.     Set oExcelApp = GetObject(, "Excel.Application")

  7.     If Err.Number <> 0 Then

  8.         Set oExcelApp = CreateObject("Excel.Application")    

  9.         DoEvents

  10.     End If

  11.     Err.Clear

  12.  
  13.     Set oExcelwk = oExcelapp.Workbooks.Open("[yourexcelfile.xls]")

  14.  
  15.     oExcelwk.Activate

  16.     oExcelapp.Visible = True

  17.     MsgBox "OK"

  18.     oExcelwk.Close False

  19.     oExcelapp.Quit

  20.  
  21. End Sub

use above code to test opening file excel