如何计算字符串中的逗号个数呢？谢谢！

Private Sub Command1_Click()
Dim rens$
  rens = IIf(Right(Text10.Text, 1) = ",", Left(Text10.Text, Len(Text10.Text) - 1), Text10.Text) 
  rens = IIf(Left(rens, 1) = ",", Right(rens, Len(rens) - 1), rens)  
  Dim ContRS As Integer
  Dim JiShu As Integer
  JiShu = 0

  For ContRS = 1 To Len(rens) Step 1
  If Left(rens, ContRS) = "," Then
  JiShu = JiShu + 1
  End If
  Next ContRS
  MsgBox JiShu
End Sub

1、上面代码我想通过对一串字符串进行判断，看其间是否有逗号“,”，并计算有几个逗号，但是怎么计出来都是0呢？（头尾的逗号不算，前两句我已经把头尾的逗号去掉了。

2、在VB的text文本框中，如何限制只能进行删除操作，而不能进行输入操作呢？谢谢！

VB code

Option Explicit

Private Sub Command1_Click()
    Dim strA() As String
    strA = Split(Text1.Text, ",")
    Debug.Print UBound(strA) - LBound(strA)
End Sub

Private Sub Form_Load()
    Text1.Text = "jdkjfkdjf,dfjdkfjdk,dfd,dfdk,dfjkdf,dfjkd,fjkdf,hei,shal,kk"
End Sub