Удаление букв и определенных символов

Imports System.Math 'connection of math library
Imports System.Char 'connection of char structures library
Public Class Form1
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        End
    End Sub
 
 
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
 
    End Sub
    Private Sub TextBox1_KeyPress(ByVal sender As TextBox, ByVal e As KeyPressEventArgs) Handles TextBox1.KeyPress
        Dim chr As Char = e.KeyChar
        Dim iCh As Integer = AscW(chr)
        If Char.IsLetter(chr) AndAlso (chr <> vbBack And chr <> ChrW(32) And iCh + iCh <> 52 And iCh + iCh <> 48 _
            And iCh + iCh <> 44 And iCh + iCh <> 2 And iCh + iCh <> 6) Then e.Handled = True
    End Sub
 
    Private Sub TextBox2_KeyPress(ByVal sender As TextBox, ByVal e As KeyPressEventArgs) Handles TextBox2.KeyPress
        Dim chr As Char = e.KeyChar
        Dim iCh As Integer = AscW(chr)
        If Char.IsLetter(chr) AndAlso (chr <> vbBack And chr <> ChrW(32) And iCh + iCh <> 52 And iCh + iCh <> 48 _
            And iCh + iCh <> 44 And iCh + iCh <> 2 And iCh + iCh <> 6) Then e.Handled = True
    End Sub
 
    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        Dim x, y, j, c, n, cast As Double, p As Single, k As Integer
        Dim s1, s2 As String
        x = TextBox1.Text
        y = TextBox2.Text
        If (x = 0) Or (y = 0) Or (x = 6) Then
            MsgBox("Error")
            TextBox1.Text = ""
            TextBox2.Text = ""
 
        ElseIf x <> 0 Or y <> 0 Or x <> 6 Then
 
            cast = Abs(x - 6)
            c = x * Math.Log10(cast) - ((Sin(x) * Sin(x))) / (y * (x ^ 3))
            p = c
            k = c
            j = Fix(c)
            n = Int(c)
            s1 = c
            s2 = p
            TextBox3.Text = c
            TextBox4.Text = k
            TextBox5.Text = j
            TextBox6.Text = n
            TextBox7.Text = p
            TextBox8.Text = c + p
            TextBox9.Text = s1 + s2
        End If
    End Sub
End Class

Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
        If Not Char.IsDigit(e.KeyChar) AndAlso e.KeyChar <> vbBack AndAlso e.KeyChar <> "-" AndAlso e.KeyChar <> "," Then e.Handled = True
        If e.KeyChar = "," Then
            If sender.Text.Contains(",") Then e.Handled = True
        End If
    End Sub