loop until a file name is entered in a save that does not already exist

I have the following code at the back side of a macro to copy some of the contents of a workbook to a new workbook and to save the new workbook with a file name that the user has to enter. I want to prevent the user from overwriting a file with the same file name in a loop until the user enters a unique file name. Here is the code I have so far:

Set NewBook = Workbooks.Add
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False
Selection.PasteSpecial Paste:=xlPasteFormats, Operation:=xlNone, _
SkipBlanks:=False, Transpose:=False
Selection.ColumnWidth = 10.57
Sheets("Sheet2").Select
ActiveWindow.SelectedSheets.Delete
ActiveWindow.SelectedSheets.Delete
Do
fname = InputBox("Type in the Reference Number shown at the top left hand portion of your screen now.")
Loop Until fname <> False
NewBook.saveas Filename:="\\mrbcapa\CAPA File\CAPA# " & fname
ActiveWorkbook.Close

Workbooks("MAF-8.5-0.XLS").Close SaveChanges:=False

At the NewBook.save as, if the file exists, you get the standard Excel message box that the file already exists and do you wish to overwrite.

I want the code to disallow this option and simply loop asking for a unique name until the user enters a unique file name.

Maybe this will help.

http://www.excelguru.ca/content.php?...Folder)-Exists