first by using "call es_date_time_type(i1, 7)" you are looking for a
sub es_date_time_type
....
end sub.

What I gave you above is a function that needs to be used before the update code.

i1 = trim(request.form("date_time_field")
i1 = es_date_time_type(i1, 7)

then your sql update

i changed my codes to these:
<script for="textfield" language="VBScript" event="Onkeypress">
            Dim i1
            i1=Document.form1.textfield.value
            i1=es_date_time_type(i1,7)
            Document.form1.textfield.value=i1
            </script>
but it is still give me such error

why do you use JavaScript to achieve this?

can you not do the changes before update call?

the values that change before update are old values and when user change those valuse the valuse that the users changed should be insert to database.so i think i should do changes at the time that the update call.ofcourse I don't know is it a correct way or no.I like to uniderstand if there is a good way for do that.
thank you again because of your useful help(user can now update their new values if they enter yyyy/mm/dd format but if they want just to update one of dates they should change others too.because the old dates that tey entered them before are shown as:dd/mm/yyyy and sql doesn't accept these.

when they want to update, you should convert the old values as well using the above function.
All this should happen before the sql update statement, or you could use the function to display the old values the way you want to be inserted into the database.

<input type="text" value="<%=es_date_time_type(your_rs_value,7)%>" name="your_name" />

Thank you very very very much:)it is working now and i learned many useful things from you.

glad i could help