while loop stopped by key press

Hello,

I am building an applitation that in one time  in loop collects a data from multimeter and displays it on .uir panel.

I have a probelm with breaking this loop. I want to do that by pressing any key, but it does not work.
I figured out that when program is in that loop, there is no callback recognized.

I have tryied with GetUserEvent, but it has not worked. 

It could be also a solution to have a callback that generates every 0,5s and refreshes that data, but I do not know how to do that.

Code:

/////////////////////////////////////////////////////////

int eventPanel, eventCtrl;
QueueUserEvent (2000, panelHandleFILTER, FILTER);
do{
...

eventPanel= panelHandleFILTER;
GetUserEvent (0, &eventPanel, &eventCtrl);
}while(eventCtrl!=2000);

//////////////////////////////////////////////////

Best

Chris