Recording Data To A List?

Am new to the VB platform and have only been messing around with 2008 for a few months,off and on.Have built a rotational inertia based Dynamometer for personal use in my R/C hobby.Have written some code that allows me to read roller frequency,that is then figured to roller RPM,and eventually ,vehicle ground speed.

Now before anyone shoots me down,( I don't mean this to be sarcastic,but I have received negativity on other forums) I know that ,because of various interupts on my P.C.,that the windows timers aren't all that accurate,causing me to miss incoming signals that screw up my measurements, and the best thing is an external aquisition unit.Let me just say that I run my VB program parallel to an external frequency counter,and have at any given time a difference of max. 8 hz at higher revs.Also I use an external timer based counter that figures the ground speed ,and it also is within a half KmH.This is only a hobby for me and that's close enough.Someday I may build something that does the computing externally and gives it to VB,but for now.........So now to the good part

Here's my question: How can I write code that will let me record the RPM ,from TextBox2, at each timer interval,and have them listed?

I need this to calculate the RPM changes per interval in order to establish "angular acceleration" ,for further calculations.

In Addition,I need a way for my program to know when something changes or does'nt.If I start my programm and don't run the dyno ( no signals) then it will start saving a bunch of zero's that I don't need,and when I get to the end of the run,the RPM will top off(no change in signals)but keep saving.The best would be,start recording when the 1st signal is detected and stop recording when the signals stop changing, and tell me I can stop.
But I'm not that advanced.........yet.

The next problem is that I have no idea,depending on what vehicle I test, how many intervals will be recorded, as one may or may not take longer to reach max.RPM.

Heres what I have so far:

Public Class Form1
Dim product1 As Double
Dim product2 As Double

[code]...