Further inquirys give the following results:
When the programs are running (the total system), and I change the filename of Calculations.js (say to Calculations_test.js) the folowing happen's:
The program keeps running good as long as I dont change the view (or refresh the page)
When I press F5 (refresh) then there comes an alarm message " ScripFault" (the picture is in Dutch)
meaning "the value of the item covertValue null or not defined and no function"
This should mean ( as far as my knowledge go's) that the script in Calculations.js is putting a little program with an name of "convertValue" in the computer and run it ??