Web Services function call and data refreshing
 

Has anyone thought up a way to preiodically refresh the results of a cell's
function? I built a web service and a function for my end users to call and
return some data. The data on the back end changes quite often and I'd like
to be able to update all the cell data to refresh the function results on
each cell in which its called. Is there a way to force a cell to refresh or
execute its function on workbook open?

Thanks,
Jon