One question, are you sure you will give the possibility to ANY user to RELOAD your app at any times?
what is the objetive?
you can not resolve with a diferent solution?
I said this because it is not the best option to give to any user this "power" and this posibilty, think that any user at any time will have the possibiity to reload the app when they wants and the the concurrency and the permonce will not be the best it depends on the time of the reload have.
It is not a good practice to provide the option to reload the Dashboard on demand, it will have lot of performance issues. Instead you can increase the refresh frequency every 15 minutes, 30 minutes etc based on the requirement in the Qlikview server.
Still if you want to provide this option you have to use EDX triggers for this. Check this links below