how can i do to return a value of a field selected in a dbgrid.

I do a query, then i show the result in a dbgrid, then the user can selected one fields by doublecliking on it, but how i take this value....

one problem, is my dbgrid has 8 fields, but after i work with only one fields..

Another question,how should i print the data in a dbgrid..without printing all the form.

Thanks a lot...