[excel] How to open a workbook specifying its path

Sub openwb()  
    ChDir "E:\sarath\PTMetrics\20131004\D8 L538-L550 16MY"
    Workbooks("D8 L538-L550_16MY_Powertrain Metrics_20131002.xlsm").Open    
End sub

Here, I am getting an error saying Subscript out of range on 3rd line. What should I do to open a workbook specifying its path?

You can also open a required file through a prompt, This helps when you want to select file from different path and different file.

Sub openwb()
Dim wkbk As Workbook
Dim NewFile As Variant

NewFile = Application.GetOpenFilename("microsoft excel files (*.xlsm*), *.xlsm*")

If NewFile <> False Then
Set wkbk = Workbooks.Open(NewFile)
End If
End Sub