I have an invoice form where I'm giving the user opportunity to apply coupons to the invoice total. These coupons are held in another Model and I am going to do a lookup on the Coupon code (something like "20OFFONFRIDAY") which I will use to find what the restrictions and benefits of the coupon. (and to see if it even exists at all) The invoice does not have "coupon_code" on it so I hand forged the field onto my form with html: <% if (@invoice.status == 'new') %> <input id="coupon_code" name="coupon_code" type="text"/> <% end %> and I am calling a controller method with link_to and would like something like the following jquery enhanced link_to to work: <%= link_to "Apply Coupon", { :controller=>"invoices", :id=>@invoice.id, :coupon_code=>$('.coupon_code').val(), :action=>"apply_coupon_code" }, :method=>"post" %> ^formatted for easier reading Then inside my "apply_coupon_code" method I will go off to a couple other models and perform business logic before returning the updated invoice page. ...but maybe it's a pipe dream. I guess if push came to shove I could add the "coupon_code" field to my invoice model (even though it's persisted elsewhere.) so it's part of the entity and thus easily available on my form to send back into a controller, but I just hate adding a column to make a coupon validation easier. I figured I'd ping stackoverflow before taking that path.