Sub main()

Dim i As Integer
Dim wrk As Workbook
Dim wsh As Worksheet, wrk_Name, wsh_Name, prmpt As String

prmpt = "Enter Workbook name:"

wrk_Name = Application.InputBox(prmpt)

prmpt = "Enter Worksheet name:"

wsh_Name = Application.InputBox(prmpt)


Set wrk = Workbooks(wrk_Name) 'This line gives error

'....
end sub