Option Explicit

Private Sub Command1_Click()
Dim i As Integer

Dim Losen As String

For i = 1 To 20
If i Mod 2 > 0 Then
Losen = Losen & RandomChar(65, 90)
Else
Losen = Losen & RandomNum(0, 10)
End If

Next i
MsgBox Losen
End Sub

Module:

Option Explicit

Public Function RandomChar(Lower As Integer, High As Integer) As String

Randomize
RandomChar = Chr((High – Lower) * Rnd + Lower)

End Function

Public Function RandomNum(Lower As Integer, High As Integer) As Integer
Randomize
RandomNum = ((High – Lower) * Rnd + Lower \ 1)
End Function