not sure what you want. you typically never leave the page with calculators but just resubmit to itself on each event or user entry. although ASP wouldn't be the best for a calculator. I would use a client level scripting langauge like javascrit.
if you do want ASP then all you need to do is set the form fields to have a value with the form object
eg:
<input type="text" name="cost" value="<%=request.form("cost"

%>">
then have a onBlur event along with the submit button to do that auto update feature in that specific link. along with a hidden field to catch the submission
so
<input type="text" name="cost" value="<%=request.form("cost"

%>" onBlur="submitFrm()">
javascript comes in as
function submitFrm() {
document.submission.value = "yes";
document.formname.submit();
}
then in the initial read of the page do some calc's
<%
If Request.Form("submission"

<> "" Then
calculator the values given a value passed
Else
%>
load the form again (all the HTML)
<%
End If
%>
and so on with each field.
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Hakuna matata!!