Formula for different yearly periodicity

[Ruthanne]

Thank you in advance for your time & help. I am hoping this is simple but I am having a hard time wrapping my head around this.
I am trying to automate a chart that figures out what year a maintenance task is due. The tasks' periodicity varies from every 12 month to every 72 months. The maintenance "start date" was 2008 and I used a formula something like this (=IF(MOD('behind the scenes'!$G$5/$R30,1)=0,"yes","no") where $R30's input was either 12, 24, 36, 48, 60 or 72 and $G$5's permanent input was 36 (since this year, 2011 is 36 months after the 2008 start date)....BUT...my problem now is that new tasks have been added since 2008 so their start year is either 2009, 2010 or 2011.
I'm thinking I can use a simple formula (to determine if maintenance is due this year) in one cell (without needing a vlookup or something else) that is something like this:
=IF(($Q$21+($R21/12)=2011,"yes","no") where $Q$21 is the start year of the maintenance start point & $R21 is the month periodicity (12, 24, 36, etc) but again, can't quite wrap my head around this. Maybe a formula like =IF(INTEGER(($Q$21+($R21/12)),"yes","no") so it is looking for a whole number?

Hmmm....any ideas?

Much thanks!

 

[barry houdini]

I would think this one would work

=IF($Q$21+$R21/12=2011,"yes","no")

R21/12 will always be an integer anyway, if R21 can only be a number divisble by 12......

 

[Ruthanne]

Much thanks Houdini...I will try. I bow down to the smarts of the contributors on this forum and give thanks for the many hours you so graciously give of your time & brain power. I truly appreciate it. Y'all have helped me with some really hard ones that I could have never begun to figure out myself! THANKS SO MUCH!

 

[Ruthanne]

This worked lovely (after trying to "model" the formula after the previous "MOD" function):
=IF(MOD((W$1-$Q21)*12/$R21,1)=0,"yes","no")
where:
W$1 was column heading for a particular maintenance year (2011 in this case)
$Q21 is the year periodicity started (2008 in this case)
$R21 is the periodicity (for example=12, which means maintenance is required every year)

The problem with =IF($Q$21+$R21/12=2011,"yes","no") is...(for example)
$Q$21 is 2008, the year periodicity started
$R21 is 12, the periodicity, so in this example the maintenance should be done every year but the calculation would be
=IF(2008+12/12=2011) then "yes" if true, "no" if false. Well 2008 plus 1 is 2009, not 2011 so I am getting a "no", maintenance is not required...ooo my head hurts.

Anyway, thanks everybody so much for all the other times you have propelled my Excel projects to completion!!!!!!!!!