Could someone please tell me whether the following is possible?
I'm especially murky about step #5 :-)

I'd be very grateful for pointers to an online step-by-step
article showing something similar, or to an excellent book dealing
with javascript/ web services/ proxy methods/ ado.net datasets and
how to avoid postbacks.

1. user enters a string into textbox

2. user clicks standard HTML button on form, launching javascript
function.

3. javascript function grabs string from textbox, builds query
string with the textbox text, and invokes a web service, passing
it the text string as a lookup value.

4. web service searches a database, and then

5. web service returns ado.net dataset to a proxy method
running server-side, which places the dataset in a session
variable and invokes the databind() method of a web-control on the
form (e.g. ASP.NET grid or 3rd party multi-column combo) binding
the control to the dataset

Thanks!
Tim