You are starting to get into more complex programming!
This will open the first file whose name starts with "Presentation" in a folder.
I wouldn't make the folder "C:\" and I would consider a different prefix than "Presentation"
Here's the basic of finding a matching file name using the File Scripting Object (fso).
Code:
Sub WildCard()
Dim fso As Object
Dim oFile As Object
Dim oFolder As Object
Dim FolderPath As String
Dim opres As Presentation
FolderPath = "C:\"
Set fso = CreateObject("Scripting.FileSystemObject")
Set oFolder = fso.GetFolder(FolderPath)
For Each oFile In oFolder.Files
If oFile.Name Like "Presentation*" Then
Presentations.Open oFile.Path
Exit For
End If
Next oFile
End Sub