>If I Make Properties Local to a screen, they are treated separately and dont interfere with a second instance of the same screen at the same time ..right ?

Correct. When you use "thisform", it is referencing the curent instance of the form.

>If I make all the Memory variables lcoal,by looping around every field in a particular file, will these memory variables not then be local to the screen and not interfere with a second instance. If this is the case, I should not need to set up a Screen object to hold the memory variables ?

I'm not sure what you mean here. Sergey's approach doesn't involve local variables, just a property of the form.