Simple Form w/ Edit Button

[George]

I want to build a form where each entry field is either pre-populated
with data from SQL and 'Read Only' (doesn't have to be 'readonly'
strictly speaking but I don't want it to be editable, like a textbox
that's disabled or a label) with an 'edit' button next to the field that
makes it editable, or if there is no data for the field, have it be an
editable textbox.

The wrinkle is that I want the 'edit' buttons
to work client-side.  I've tried javascripts that toggle the 'readonly'
attribute of textboxes, (which I couldn't make work) and I've tried
javascripts that enable/disable the textboxes (which also didn't work). 
Someone the problem I had with these first two approached were with
poastback.  I want to retrieve the value from each field whether it's
been edited or not at postback, and I want the value to return as
whatever it has been changed to after postback.  I had trouble with
both.

I've even tried having two controls, a label and a textbox,
with linked values where only one of the two is ever visible.  I had
trouble getting this approach to render correctly using client-side
code.

Is there an approach that is 'best practice' or that most people use for this?

Thanks.