Calculate date based on number of hours

Hi all,

I'm trying to calculate the due date of maintenance needed based on the number of hours the machine is ran... I had it all setup by months, but was recently told to change it (because we may work more or less depending on work load). Basically, every morning I enter in the number of hours on the machine, and it needs to tell me the due date based off that. This is what I WAS using...

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What is the easiest way to add a row for the number of hours as the frequency due, and convert it to using that?

Thanks!

The machine I am running has an Hours meter on it. I would enter in one generic place the current number of hours that is on the machine IE: right now there are 33,569 hours on it, lets say this number is stored in B3 just because I like it centered . Then for each item that needs maintenance, have the task listed in Column A, the number of hours the machine had on it in the last time maint. was done in column B, the number of hours allowed between each maintenance in column C, and the calculated date maint is due again in column D. Its actually quite hard to type this lol, I'm confusing myself...

Current hours on machine
Maint due - Hours last done - Hours between maint - Calculated due date

Thanks!

The machine does not run a set number of hours a day and we work random overtime on days off, so a set formula like that would not work

Thanks though!