Hi,
I try to implement it, but do not encounter your problem.
In mainvi
1. Pass mainvi reference to a global.
2. Insert subvi reference to sub panel.
3. Run subvi by reference and do not wait until done.
In subvi
1. All in a infinite while loop.
2. Read mainvi reference from global.
3. Set cursor busy.
The only problem I encounter is that since the cursor is set busy in mainvi, it is unable to close the mainvi by click Abort Exec button. 🙂
I don't think it is a good idea to set cursor busy steered by the subpanel vi.