Set progress on operation

we can show the progress of the operation using following code
static void Progress(Args _args)
{
PurchTable _purchTable;
PurchLine _purchLine;
#Macrolib.AviFiles
SysOperationProgress progress = new SysOperationProgress();
;


progress.setCaption("Task");
progress.setAnimation(#AviUpdate);

while select _purchTable join _purchLine where _purchLine.PurchId == _purchTable.PurchId
{
progress.setText("Purchline is getting");//this will show the operation progress
}






}