How to set value to a control

Hi,

I am doing a site in SF5. In this site, there are lot of pages having a common 
section displaying a contact form.The issue is that
all the fields in these pages are same except a hidden field, say CostId.
Since this CostId is different for each page, I need to create several pages
with same fields with only difference being the value of CostId.


To avoid creating the creation of several pages, I want to create a form control which accepts CostId as parameter. How can this be done? ie. I would like to be able 
to drag/drop this form control on the placeholder and then set the CostId.


The functionality is amost similar to FormsNotification scenario. ie instead of Email settings, I need to set CostId while dragging the control to the palceholder.


Can anyone please help me.


Thanks,
Surya.