mikeyc - You will also need the full path to the source workbook

VB Code:
  1. Sub CreateLink()
  2. Dim sSourcePath As String
  3. Dim sSourceBook As String
  4. Dim sSourceSheet As String
  5. Dim sSourceRange As String
  6. Dim sFullAddress As String
  7.  
  8.     sSourcePath = "C:\Files\" 'Put the complete path to you source workbook here
  9.     sSourceBook = "YourSourceWorkbook.xls" 'put the name of your source workbook here
  10.     sSourceSheet = "YourSheetname" 'put the name of your sdource worksheet here
  11.     sSourceRange = "B12" 'put the address of the source cell here
  12.        
  13.     sFullAddress = "='" & sSourcePath
  14.     sFullAddress = sFullAddress & "[" & sSourceBook & "]"
  15.     sFullAddress = sFullAddress & sSourceSheet & "'!"
  16.     sFullAddress = sFullAddress & sSourceRange
  17.    
  18.     Range("C1").Formula = sFullAddress 'Put the cell where you want the link here
  19. End Sub