Sub Test()
r = 0
For n1 = 65 To 87
For n2 = n1 + 1 To 88
For n3 = n2 + 1 To 89
For n4 = n3 + 1 To 90
r = r + 1
Range("A" & r) = Chr(n1) & Chr(n2) & Chr(n3) & Chr(n4)
Next
Next
Next
Next
End Sub