I don't know what teechart pro is except for some activeX control you found somewhere.
But a couple comments. Be careful with the way you close all those activeX references. You should close them in the reverse order that you open them. As your code is right now, you are closing some of your higher level references in parallel with some of your lower level references. For example, in your for loop, you close the reference to ITchart at the same time you are still using the reference to Series you obtained from that. You should close Series first, then later close ITchart. Most of your property nodes and invoke nodes do not have the error wires connected. If you did, you would be able to enforce the order of execution of when the different levels of references close.
In general, you should only close the references after the loops are done. Constantly opening and closing the references will slow down your code. And if those ActiveX controls contain any sort of memory leak, you will be slowly losing memory and that will make things seem to run slower the longer the VI runs. There are some reference wires that you never seem to close.
You may also want to put some timing functions in your loops so you can see how long each loop iteration is actually taking to see if the loop iteration time is growing.
