How to calculate keyhold time (in milliseconds) of a keypress & inter-key latency time between 2 keys using vb in asp.net

Hi, I'm newbie with asp.net & just have self-learning a few months ago...
I've tried to understand how to implement my idea into .net programming. I've done all parts except the keystroke part.
I would like to calculate the keyhold time of a keypress in ms & also the inter-key latency time between 2 keys.
 
The idea is as below:
key 'A' is pressed (keydown) - record keyhold time
key 'A' is depressed (keyup) - record keyhold time
key 'A' is pressed & key 'B' is depressed - record inter-key latency time
 
And also, I need ideas how to put my keystroke data into database. Should I record the key character also??
Example: A.down.time || A.up.time || A.B.time
 
Tq. . . v(^_^)//