The system variables are only updated when a reload is performed so I do not think that will give you the dynamic ability you are after.
What I have done is add three new variables (format, decimal separator and thousand separator) and mapped these to your buttons. In the table I have set the number format to Expression Default and modified the expression to include the Num function which calls in the values stored against the variables and allows for the dynamic formatting to work.
Hope this helps.
issue.qvw 170.2 K
as a result of what has been remarked here, the only possibility for Qlik View to dynamically change number format,or dates format, which would be usefull in multi country projects, is to use the Num function (or Date function).
Of course this limitation has some side effect: each Expression (or Dimension containing dates) in the QVW application must be set up as a Num-function-expression, however this is not correctly manged by QV for bar chart axis, where it seems that the Default number expression is used instead of the Expression format.