C# using VB4.0 in Silverlight Application - TextBox input quirky

[Nikip04]

I am using the below code and when testing it, the textBoxes will allow number input, but you have to enter the complete number, then arrow back to enter the decimal. Otherwise the cursor jumps in front of the first number and will not allow the decimal to be entered. I would also like to allow the $ to be inputted first.

Any ideas how I can customize this textBox to do these functions allowing the calculations to function properly given below?

private void textBox1_TextChanged(object sender, TextChangedEventArgs e)
{
    //Adding ToolTip
    ToolTipService.SetToolTip(textBox1, "Enter Price, numbers first, then arrow back to add decimal.");

    if (Double.TryParse(textBox1.Text, out value1))
    {
        textBox1.Text = value1.ToString();
    }
    textBox69.Text = value69.ToString();
    if (textBox1.Text == null || textBox1.Text == "") value1 = 0;
    {
        textBox1.Text = value1.ToString();

        if (textBox1.Text.EndsWith(".97") == true)
        {
            value20 = 0; value36 = 0; value69 = 0;
            textBox20.Text = value20.ToString();
            textBox36.Text = value36.ToString();
            textBox69.Text = value69.ToString();
        }
        if (textBox1.Text.EndsWith("1") || textBox1.Text.EndsWith("2") || textBox1.Text.EndsWith("3") || textBox1.Text.EndsWith("4") || textBox1.Text.EndsWith("5") || textBox1.Text.EndsWith("6") || textBox1.Text.EndsWith("8") || textBox1.Text.EndsWith("9") || textBox1.Text.EndsWith("0") == true && (value1 < 100.00))
        {
            value69 = 1;
            textBox69.Text = value69.ToString();
        }
        if (value1 > 100.01 && value1 < 149.99)
            value69 = 2;
        textBox69.Text = value69.ToString();
         }
            if (value1 > 149.99)
            {
                value69 = 3;
                textBox69.Text = value69.ToString();

    }
}