dynamic search of custom field

I have installed version 4.2.10.
I imported and updated the older (version 3.8.4) RT database.
So far all seems to be working fine.

I have a custom field on my Ticket/Create.html page (Customers) which is a
'Select one value' Select box, is loaded using a package
(RT::CustomFieldValues::Customers) located in
rt4/local/lib/RT/CustomFieldValues and contains a very large number of
customers.

I have added a text box above this select box (named 'Search Customers') and
would like to modify the contents of the select box each time the "keyup"
event is fired for this text box; and base the query which loads the select
box with a where clause similar to "where customer_name like '%<text field
content>%'.

I just can't find out what I need to do to 
1)	reload the Ticket/Create page on the 'Select Customers' keyup event;
and
2)	pass the text box content (value) to the query in
RT::CustomFieldValues::Customers.

Any assistance with this would be greatly appreciated.

Thanks,

Mike