Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
    e.Handled = NumbersOnly(e.KeyChar, TextBox1)
    End Sub

    Private Function NumbersOnly(ByVal pstrChar As Char, ByVal oTextBox As TextBox) As Boolean
 
    If (Convert.ToString(pstrChar) = "." And InStr(oTextBox.Text, ".")) Then Return True 'accept only one instance of the decimal point
    If Convert.ToString(pstrChar) <> "." And pstrChar <> vbBack Then
    Return IIf(IsNumeric(pstrChar), False, True) 'check if numeric is returned
    End If
    Return False 'for backspace
    End Function