validation and message box

[Newbie]

i have a c# asp.net webform wherein i'm using requiredfieldvalidator and
regularexpressionvalidator controls to validate the textboxes. i have a
button "Close" that should work like this: When the user clicks "Close", a
message box appears asking "Do u want to save this...? Yes|No". if the user
clicks "yes", the requiredfieldvalidator and regularexpressionvalidator
controls will validate the data in the textboxes and save them in the
database and the user is redirected to another webform. if the user selects
"no", then no validation occurs and the user is redirected to another
webform. i'm using javascript for the message box:

<script type="text/javascript">
function Close(){
var agree=confirm("Do you wish to save changes?");
if (agree)
var result = false ;
else
var result = false ;
}

the problem is this:
in the property window of the "Close" button, there is a property called
"causesvalidation". if i set this to true, the requiredfieldvalidator and
regularexpressionvalidator controls are able to validate the textboxes but
the message box (via javascript) is not being called. if i set this to false,
the requiredfieldvalidator and regularexpressionvalidator controls are not
able to validate the textboxes but the message box (via javascript) is being
called. it's one or the other but not both at the same time. how can i fix
this? is there another function similar to confirm( ) that presents the user
with yes and no buttons instead of ok and cancel buttons? thanks in advance.