vb求程序：四个文本框，随机填入字母？

'在窗体上添加TextBox数组，名字为Text1
Private Sub Form_Load()
Dim I As Long, J As Long, K As Long

For I = 0 To 3
Text1(I).Text = vbNullString
Next I
Randomize
Do While K < 100
I = Rnd * 3
Text1(I).Text = Text1(I).Text & Chr(Rnd * 3 + 65)
K = K + 1
Loop
End Sub

Private Sub Command1_Click()
Dim a(0 To 3)
For i = 0 To 3
a(i) = Int(Rnd * 26) + 65 '65 到90 ASCII码 A~Z
Next i

Text1.Text = Chr(a(0))
Text2.Text = Chr(a(1))
Text3.Text = Chr(a(2))
Text4.Text = Chr(a(3))
End Sub

Private Sub Form_Load()
Text1.Text = ""
Text2.Text = ""
Text3.Text = ""
Text4.Text = ""
End Sub

Private Sub Command1_Click()
Dim a() As Integer, i As Integer, b(3) As String, k As Integer, S As String
b(0) = "A"
b(1) = "B"