With time constraint it's easy. Just save hours into an integer variable and then use constraints. For example if hours > start hour variable and hours < end hour variable. Of course you could also have minutes variable and add some constraint to these too. You need to play with these numbers and constraints.
About the trigger you could use time interval for every minute and after trigger fires save hours and minutes into a variable and check if they are equal to your hours and minutes.
Another way would be to use stopwatch which support variables and start them at midnight, than on every change of your hours and minutes calculate total seconds as hours*3600 + minutes*60 and save into variable called for example total seconds and use that as a trigger time for stopwatch trigger.
These are not full solutions. There are things you would need to tinker with. I am just suggesting that there are a creative ways how to solve your problem.