Hi,

1. Adding a general Parameter.
 -Once you have run the query, right-click a cell in the returned data and choose EditQuery from the pop-up menu.
 -There, change the url
        http://finance.yahoo.com/q/ks?s=PFE
   to
       http://finance.yahoo.com/q/ks?s=["Stock1","Enter stock symbol."]      
  -click OK
  - You are now being prompted to enter a stock symbol

Note: if you had saved your query into a qry file, i am not sure it will update the file and you may loose any modification. In that case, rebuild your query without saving it into a qry file.

2. Change the Parameter type.
Now that you have built a general parameter (prompt box), when you right-click the query data, the 'Parameters' submenu in the pop-up menu is enabled.
There, you can change the type of the parameter to be linked to a cell.

I hope this helps,