Check for file during archive - vb from excel

I have a macro which copies files from one directory to another only if the following condition exists:
Costs*.xls.  If there are no files in the source directory, the vb script produces an error message that I do not want the users to see.  Is there any way to display a message box that says there are no files that meet the archive criterion?  I have attached my macro for your review.

Sub ArchiveFiles()
    Dim fso As Object
    
    Dim sSourceDir As String
    Dim sTargetDir As String
    
    sSourceDir = "C:\my documents\"
    sTargetDir = "C:\my documents\backup\"
    
    Set fso = CreateObject("Scripting.FileSystemObject")
    
    fso.movefile Source:=sSourceDir & "Costs*.xls", Destination:=sTargetDir
    fso.movefile Source:=sSourceDir & "Status*.xls", Destination:=sTargetDir
    
End Sub

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