Hi Andreas.
When you say two arguments, the second argument is perhaps the classname:
w_detail lw_window
Open ( lw_window , 'w_mythirdreport' )
(Where w_mythirdreport is a descendant of w_detail)
The point is, to have multiple windows open, you need a local variable. If you use the window class name, you are using a global variable and the second open with just set focus to that.
hth Lars