Timer function to display HH:MM:SS

I have a field that is in minutes, where the max minutes could be 240-300

I want to display on label1.caption a countdown showing hours:minutes:seconds

The user presses a start button to start the timer which will pull the time in minutes from a field called goal

I need this countdown to continue until they press the finish button and need the countdown to continue into negative numbers if it goes below zero before they press the finish button.

Example: goal time is 90 minutes. I need it displayed on the label as 01:30:00 and countdown in 1 second increments and stop when they press the finish button. If it goes below 00:00:00, I need it to display -00:00:01 and continue to count down, increasing the negative value until they press the finish button.

Thank you