Verifying format of entered phone number

Hi!

I am calling a javascript from this xsl snippet that the entered telephone number is in a certain format: 123-456-7890
I would like the code to be called when the user goes to the next field.

Any ideas why this does not work?

Chuck

<td align="center">
<xsl:choose>
<xsl:when test="$aspemail != 'true'">
<INPUT maxLength="13" name="priphone" size="13" onfocus="doSubmit=false;"
onblur="checkphone(this);" value="{acct_mph}"/>
</xsl:when>
<xsltherwise>
<xsl:value-of select="acct_mph"/>
</xsltherwise>
</xsl:choose>
</td>

Javascript in calling asp page:

<script language="JavaScript">
<!--//
var doSubmit = true;
function checkPhone(fld) {
if( (fld.value != "") && (/[0-9]{3}-[0-9]{3}-[0-9]{4}/i.exec(fld.value) > -1) ) {
doSumbit = false;
window.alert("The phone number must be in this format: 123-456-7890.\n");
fld.focus();
} else {
doSubmit = true;
}
}
//-->
</script>