In my Data Sheet, I want to import Data from a datasource at run time. The problems are:

1) I go to data sheet and do sheet-->Import-->From Database. Then i write a query to select data. as soon as I finish, the a new column is created and data is fetched from data table. I want this SQL query to get executed only at runtime. How do i control when the query gets exceuted.?

2) Everytime, a new column is added to data sheet even if the same column exists. How do I populate the existing columns only?

(Please do not suggest the use of DataBase checkpoints)