Automatic Save, But Ask For New Name If One Exists

i have my excel spreeadhseet setup so that it asks me for a clients name
and then saves the file as the clients name in there folder

example:

c:work est est.xls

very often i do several differnt quotes for the same name

so when i open up and type in test as the client name, it says one called test already exists, do i want to overite it

if i do no, it ends my template
if i click yes it overrides it

how can i make it so that it says something like
the file name is already taken,
please select a new name, so id type 'test walk' or something like that, but it would know to save it in the test folder

here is the script i have now

Private Sub Workbook_Open()
MsgBox "Make sure you thank Ryan for this wonderful program which HE has created!!", vbOKOnly + vbInformation, "Notification Message"

Dim sName As String, fs As Object, sPath As String, bExists As Boolean

Set fs = CreateObject("Scripting.FileSystemObject")
sPath = "C:Documents and SettingsuserMy DocumentsWork"
If InStr(UCase(ThisWorkbook.Name), ".XLT") > 0 Then 'ask for name only if it's a template
sName = InputBox("Enter the Clients last name.", "Name Input Dialog")
If Len(sName) = 0 Then Exit Sub