Q975 How can I combine the value of two form fields, and then only pass the combined value to the server?

<script language="JavaScript"><!--
function textBuild() {
     document.formName.data.value =  document.formName.elements[1].value + ' ' + document.formName.elements[2].value;
}
//--></script>

<form name="formName" action="cgi-bin/query" onSubmit="textBuild()">
<input type="hidden" name="data">
<input type="text">
<input type="text">
<input type="submit">
</form>