Getting 'Unknown runtime error'

[UFT_Newbie]

Hi Guys,
I'm running below script and i'm getting "Unknown runtime error" at ObjWorkSheet.Rows(StartRow).Columns(Environment("Execute")).Value.

Code:

Environment("Execute")="1"

Set ObjExcel = CreateObject("Excel.Application")
ObjExcel.Visible = True
Set NewExcelfile = ObjExcel.Workbooks.Open("c:\temp\1.xls")
Set ResultFile= NewExcelfile
Set ObjWorkSheet=ResultFile.Worksheets("Sheet2")

For i = 13 To 323
    StartRow = i
ExecuteStatus = ObjWorkSheet.Rows(StartRow).Columns(Environment("Execute")).Value
If ExecuteStatus = "Y"  Then
      Browser("ABC").Page("XYZ").WebButton("EFG").Click
Else
      msgbox "Button not visible"
End If
Next

Can some please help me out with this issue.