COM

VTS_PUI1 or VTS_PI4. 

Public Function Get_List(SheetNumber As Long) As String
   '   Dim myExcel As Object
   Dim Counter1 As Integer
   Dim Returnstring As String
        Dim myWorkBook As Excel.Workbook
        Dim tworksheet As Excel.Worksheet

  '      myExcel = CreateObject("Excel.Application")
 '       myWorkBook = myExcel.Workbook.Open("C:\sample.xls")

        For Each tworksheet In myWorkBook.Worksheets
    '        Me.ListBox1.Items.Add (tworksheet.Name)
    Returnstring = tworksheet.Name
    If iindex = Counter1 Then
    Get_List = Returnstring

    End If
    Counter1 = Counter1 + 1
        Next
End Function
And try to access in vc++.Then i am getting error

Public Function Get_List(SheetNumber As Long) As String
    Get_List = "aaa"
End Function

Public Function Get_List(SheetNumber As Long) As String
    Get_List = "aaa"
End Function

VARIANT Get_List(long* number);

VARIANT _clsExcel::Get_List(long* number)
{
	VARIANT result;
	static BYTE parms[] =
		VTS_PI4;
	InvokeHelper(0x60030002, DISPATCH_METHOD, VT_VARIANT, (void*)&result, parms,
		number);
	return result;
}

_clsExcel objXl;
long ty=1;
objXl.Get_List(&ty);