enterkey

I have a form using Struts and Jstl.  My form on submit calls a struts action that reads the form and
detrmines which button is pressed and then acts accordingly.  This works great but a user pushes the enter key the action is called but
does not know which button was pressed.  Is there a way I can send in the attribute of the button when the enter key is pressed?
the form and button are below.

<ssl:form action="/loginAction.do" onsubmit="return validateLoginForm(document.loginForm)">
<td><img src="img/login_text.gif" border="0" alt=""><img src="img/clear.gif" width="5" height="10" border="0" alt=""></td>
           <td>
              <html:text property="email" value="Email Address"
                 onfocus="clearInputBox(document.loginForm.email, 'Email Address')"
                 maxlength="50" styleClass="blue_border"/>
          </td>
         
         
          <td><html:image property="loginButton" src="img/buttons/header_login_button.gif"
               onmouseover="MM_swapImage('loginButton','','img/buttons/header_login_button_over.gif',1)"
                  onmouseout="MM_swapImgRestore()"
                  alt="Login" border="0"/></td>
        </ssl:form>