You cannot do that directly in QS, unfortunately. This is one of the biggest limitations of the product, IMHO.
It is based on the nature of Qlik's components dynamic layout....
There are few options you can consider:
1. Do a mashup and use JS/HTML code to show/hide your dashboards/charts.
2. Use OMIT option in Section Access to hide specific fields (but it will just remove the data from your charts while keeping charts displayed)..
I would recommend to go with option #1. It requires significant development, but will resolve your issue.
I do not think you can do much else (as far as I know Qlik is not planning to resolve it even in 3.0 release).