Visual Basic programming

I need a simple program
I have a value that is pulled from a server directly

I need to write a simple code that compares this direct value
with the Same value it self 5 seconds ago

and Immediately the difference is at a certain value I will be notified



Example of live data:
at the hour
12:00:00 Value 100
12:00:01 Value 100
12:00:02 Value 100
12:00:03 Value 100
12:00:04 Value 100
12:00:05 The value is 50 > The difference in the value from the one before it is large, Immediately at a certain value I will be notified as a textbox