Calling upon a method to change textbox value
<p>I have a method called BuyShares() that is supposed to take a value in a textbox and add another user input value to it.  I would like to use a messagebox that sets off the method by the user clicking okay.  The only problem is that I can't seem to call upon the method. 
This is the method.</p>

<pre><code>public void BuyShares(int anAmount)
    {
        int newShares;
        newShares = GetInvestmentShare() - anAmount;
        SetInvestmentShare(newShares);
    }
</code></pre>

<p>And this is the messagebox I have set up</p>

<pre><code> private void button1_Click(object sender, EventArgs e)
    {
        DialogResult result;
        result = MessageBox.Show("Your transaction is complete", "Success", MessageBoxButtons.OK);
        if(result==DialogResult.OK)
        {
            txtStockSharesTab3.Text=??????
    }
</code></pre>

<p>This is a windows form application and the program has several different classes</p>
