Making a list of all possible combinations

I have the Letters A to U and I want to make a list of all possible combinations of 4 of these letters (e.g. ABCD,ABCE,ABCF,FGHI,TRSA and so on). The order of the letters is not important so ABCD is same as BACD.

Hope someone will be able to help.

Any help or advice gratefully received,

Jack

Here you go:

Sub Combinations()

Dim rngWriteCell As Range
Dim l1 As Long, l2 As Long, l3 As Long, l4 As Long
Dim sThisCombo

ThisWorkbook.Sheets(1).Cells.Clear
Set rngWriteCell = ThisWorkbook.Sheets(1).Cells(1, 1)

For l1 = 0 To 17
  For l2 = l1 + 1 To 18
    For l3 = l2 + 1 To 19
      For l4 = l3 + 1 To 20
        sThisCombo = Chr(65 + l1) & Chr(65 + l2) & Chr(65 + l3) & Chr(65 + l4)
        rngWriteCell.Value = sThisCombo
        Set rngWriteCell = rngWriteCell.Offset(1, 0)
      Next l4
    Next l3
  Next l2
Next l1
  

End Sub

A total of 5,985 combinations.

That is absolutely excellent thank you

Jack