Sub RandomLetters(Length As Int) As String
    Dim SB As StringBuilder
    SB.Initialize
    For i = 1 To Length
        SB.Append(Chr(Rnd(65,123)))
    Next
    Return SB.ToString
End Sub

dim str as string
str = RandomLetters(20)
lbl1.text=str

Sub RandomLowercaseLetters(Length As Int) As String
    Dim SB As StringBuilder
    SB.Initialize
    For i = 1 To Length
        SB.Append(Chr(Rnd(97,123)))
    Next
    Return SB.ToString
End Sub