Simulink slows down at line-fct, memory issue?

Hi,

I have implemented some kind of a real time plot in simulink, using an s-fct. The result is similar to the scope-block. I just connect the last and the new datapoints from the input of the s-fct with the line-command. But after a while, simulink slows down. So, I think I need to remove old line-sgements from my plot that are not visible anymore, because they are beyond the border of the figure. How could this be achieveable? Thanks.