Serial port

Question

Hello

Please i need help, i am doing a program for morse code aplication and i'm  stuck for past few days on serial port.

I have morse pad on serial port. When i press it it give some signal(logical 1). My mayor problem is how to measure how much time was the morse pad pressed.
I looked every where, i'm pretty new at vb.

I tried with loop but my program crashed, i tryed everything within my knowledge and nothing works.

I'm trying to do something like this:

if com1 is not null (that means that i have pressed morse pad, like keydown for keyboard)
start timer
when com1 is null (that means that i'm not pressing morse pade anymore, like keyup for keyboard)
stop timer

Can anyone please help me, i really need some guidance and help

best regards

Kosta