asp - серверный скрипт, поэтому наверное никак. Разве что передавать каким-то образом на сервер, но это уже будет не asp.

если тебе надо заменять запятую, то вот есть интересные решения:

And some people also use the comma as thousand separator. You'd better
define a format and refuse anything that does not fit it. With clear
rules ("." as decimal separator, perhaps space as thousands
separators, then remove the spaces and test the NaN value converting
to decimal format), you'd save yourself some work and would simplify
your users' life. Users would themselves correct the value according
to the format, ensuring the final value is the one they really want.

function validateNumber(field){
var n= +field.value.replace(/ /g,"");
if(!isNaN(n)) alert("valid");
else alert("invalid");
}

If you really want to convert numbers into javascript format, then
give
a look at the following (beware the wrapping); I'm not sure, though,
to
have covered all issues.

<script type="text/javascript">
String.prototype.toNumber=function(){
var
m_1=/^[\+-]?\d*,?(\d+(e[\+-]?\d+)?)?$/i,
m_2=/^[\+-]?(\d{1,3})?(,(?=(\d{3}))\d{3})*\.(\d+(e[\+-]?\d+)?)?$/i;
if(m_1.test(this)) return +this.replace(/,/,".");
else if(m_2.test(this)) return +this.replace(/,/g,"");
else return +this;
}

document.write(
"12.3".toNumber() + "<br \/>" +
"-12.3".toNumber() + "<br \/>" +
"12,3".toNumber() + "<br \/>" +
"120,315".toNumber() + "<br \/>" +
"120,315.".toNumber() + "<br \/>" +
"12,120.3".toNumber() + "<br \/>" +
"120.3".toNumber() + "<br \/>" +
"12,12.3".toNumber() + "<br \/>" +
"12,030,456.45".toNumber() + "<br \/>"+
",030,456.45".toNumber() + "<br \/>"+
"025".toNumber() + "<br \/>"+
"0x12".toNumber() + "<br \/>"+
"12e5".toNumber() + "<br \/>"
);
</script>

Ответ:
Thanks! I simplified it a bit and only used the n.replace(/,/,"."); which is
sufficient for my purposes. I do a calculation with the value and simply
give an error message in the result field using isNaN when letters or other
characters are used.

2monstrU
говори