Hi, this is my first post here although I have browsed the site many times for help with formulas and know-how on many things. It is a great source of information and I appreciate the time you all put into keeping it running.5 million posts are no small task.
I have searched for solutions to my problem but I'm afraid I canít find anything that helps with my current problem because of its complexity and more over because I donít know the exact terms I should be searching for.
I will try to explain. I have some farm machinery that I want to make a service list for my worker that gives him the list of jobs I want him to do every time a service is due (roughly 300 hours). And it hides the things that he doesnít need to do. I have a few machines so once I get the formula for the spreadsheet worked out, I can make this work for all of them. Mostly I want to be able to print the list, have him tick off the tasks then be able to file the lists for record keeping.
What I have done is typed all of the tasks from the operators manual into column A and then column B,C,D are when those tasks are due based on manufacture recommendations, ie 300, 600 and 1200 hours. See example.


https://imgur.com/gXAB7Zv

What I want to do is have a drop down box where he can select the intervals (300, 600, 900, 1200, 1500, 1800, 2100, 2400, 2700, 3000, 3300, 3600, 3900, 4200, 4500) and come up with some method of hiding the rows I donít need. But also need some logic in it so that when 2x services are due, ie 900hrs that will require whatever is due @ 600hr + whatever is due @ 300hr. I have come up with another matrix on my data sheet that has the combination of the 3x intervals that will make up all of the options and provide the data validation list for my drop-down box. To make it harder again, some tasks are "Check" at 300 hours, but "Change" at 600 or 1200 hours. i would like to be able to hide the respective "Check" rows if they are being "Changed" by a higher interval.



https://imgur.com/XaVyleF

My main problem is I really donít know how to make this work within excel. I have a concept in my head and I suspect I will need to use the Index() and Match() functions but the concept is too much for me.
Does anyone have any suggestions on what functions I should be looking at or a similar concept somewhere? I would rather try to learn what needs to happen than simply copy and paste someoneís solution.

Thank you in advance.