Lookup & open file based on partial filename

Come again???

Does this help ?

Public Sub demo()
  ' Config Here !
  FullPath = "C:\test\"
  FileName = "*" & "Book" & "*" & "Mar" & "*"
  FileExt = ".xls"
  
  Call OpenFile(FullPath, FileName, FileExt)
End Sub

Public Sub OpenFile(FullPath, FileName, FileExt)
On Error GoTo exitloop
 NextFile = Dir(FullPath & FileName & FileExt)


Do While NextFile <> ""    ' Start the loop.
   NextFile = Dir
   Workbooks.Open FileName:=NextFile
Loop
exitloop:
End Sub