Enter button does not submit form (IE ONLY) ASP.NET

I have a form with a textbox and a button. IE is the only browser that will not submit the form when Enter is pressed (works in FF, Opera, Safari, Chrome, etc.). I found this javascript function to try to coax IE into behaving; but no avail:

function checkEnter(e){
    var characterCode
    if (e && e.which) {
        e = e
        characterCode = e.which
    } else {
        e = event
        characterCode = e.keyCode
    }
    if (characterCode == 13) {
        document.forms[0].submit()
        return false
    } else {
        return true
    }
}

Implementation:

searchbox.Attributes("OnKeyUp") = "checkEnter(event)"

Any advice?

EDIT: This page on CodeProject outlines what Dillie was saying, and it works perfectly.

Just create a text input in a hidden div on the page. This will circumvent the IE bug.

Example div:

    <!-- Fix for IE bug (One text input and submit, disables submit on pressing "Enter") -->
    <div style="display:none">
            <input type="text" name="hiddenText"/>
    </div>

The other thing I have done in the past is wrap the form area in a Panel and set the DefaultButton attribute to the submit button you have. This effectively maps the enter key to the submission as long as you have a form element in focus in the panel area.