Hey guys, need to have an empty field box so a customer can put in an amount and another field for an invoice number then the 'pay now' button. I have some code I was messing with below but each time I hit pay now I get an error. I've blanked out the business code for security reasons. Any help is appreciated.

<form action="https://www.paypal.com/cgi-bin/webscr" method="post" target="_top">
<input type="hidden" name="cmd" value="_s-xclick">
<input type="hidden" name="hosted_button_id" value="BLANKEDOUT">
<table>
<tr><td><input type="hidden" name="on0" value="Amount">Amount</td></tr><tr><td>
	<input name="Amount" value="0"> </td></tr>
<tr><td><input type="hidden" name="on1" value="INVOICE#">INVOICE#</td></tr><tr><td><input type="text" name="os1" maxlength="200"></td></tr>
</table>
<input type="hidden" name="currency_code" value="USD">
<input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_paynowCC_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
<img alt="" border="0" src="https://www.paypalobjects.com/en_US/i/scr/pixel.gif" width="1" height="1">
</form>