if i want to produce 3 letter combination what part of the code should i modify ?

Code:
Private Sub Command1_Click()
 Dim MyStr As String
 
 MyStr = Space$(3) 'MyStr = Space$(4)

 Open App.Path & "\3LetterCombinations.txt" For Output As #1

 For i = 97 To 122
   Mid$(MyStr, 1, 1) = Chr$(i)
   
   For J = 97 To 122
     If J <> i Then
       Mid$(MyStr, 2, 1) = Chr$(J)
       
       For K = 97 To 122
         If K <> i And K <> J Then
           Mid$(MyStr, 3, 1) = Chr$(K)
      
           'For L = 97 To 122
           '  If L <> i And L <> J And L <> K Then
           '    Mid$(MyStr, 4, 1) = Chr$(L)
           
                List1.AddItem MyStr
                Print #1, MyStr
                DoEvents
             
           '  End If
           'Next
         End If
       Next
     End If
   Next
 Next

 Close #1
End Sub