if you can turn your calculation algorithm into something which can be called iteratively, you could release control back the browser at frequent intervals by using setTimeout with a short timeout value.

For example, something like this...

function doCalculation()

{

   //do your thing for a short time



   //figure out how complete you are

   var percent_complete=....



   return percent_complete;

}



function pump()

{

   var percent_complete=doCalculation();



   //maybe update a progress meter here!



   //carry on pumping?

   if (percent_complete<100)

   {

      setTimeout(pump, 50);

   }

}



//start the calculation

pump();