I'm no guru, but do you need the path along with the file name.
Also try quotes around the sheet names

[vba]Set Wkb1 = Workbooks("Master.xls") 'change this to your desintation file name - c:\testfolder\Master.xls
Set ws1 = Wkb1.Sheets("MasterData")
Set wsD = Wkb2.Sheets("Data")
[/vba]

Hope this helps.
Mark