Position Controler when Formulas are needed to describe the position

Hi everybody, I am new and need your help.
I am working with NX 12, MCD. I have been working with NX MCD for a month.
Now I am facing several problems i can not solve myself.

1.
There is a sliding Joint which is controlled by a Position Controller.
The Joint is used to transoport tubes. The length of those tubes varies and can be adjusted via an expression (is there an other, better opportunity to do so?). Now i would like to save certain positions which afterwards can be selected via operation. Because the tubes length varies those positions are also varing therefore I need to use formulas to desecibe the Position.
For example:
Start_Pos = 400 - TubeLength
Gripping_Pos = Start_Pos +450
End_Pos = 200 + TubeLength
I managed to do so by using signals with some If / Else-condition and some boolean. 
I also managed to solve it by using an Runtime Expression. Both worked fine.
Now the main probelm is that i want to montior the cycle time of the entire process. But when I use signals or runtime expressions, in the Sequence Editor there is only shown when the boolean changes its value but not how long the parts are actually moving.
I thought about using a Joint Distance Sensor and a second Runtime Expression to controll if the target postion was achieved but that seems to be pretty laborious.

2.
An other problem I am facing concerns an Object Transformator. I want to exchange a small part for a larger part. Is there a way to controll the point where the new part is added? It seems like the the parts become exchanged at there center of mass which is not suitable in my situation

I m sorry not to give you an example file.
I Hope you understand what I tried to decribe..