Need formula for calculating future cost, every X years

Hello All,
New guy here, just getting into Excel 2013 formulas.
I am preparing a spread sheet for estimating future cost of repairs for a series of building maintenance expenses, with repairs being required in varying frequencies in the future.

I have a line 51 at the bottom of my sheet which is a listing of inflation factors for each year in the future.

For each maintenance item, I have a current (2013) cost in column E, and a frequency in column C, and a next projected occurrence in Column D.

So what I want to do for each maintenance item is to project the future cost of each maintenance item (Column C) at the next projected due date (Column D), inflating the current cost (Column E) by the inflation factor in each column shown in Line 51, then repeat the inflated cost at the frequency in Column C. Future years are in Line 4.

e.g. It costs $1,000 to repair sprinklers in Line 37 of attached spread sheet. Repair is due in 2018, and the inflated cost is $1,000 times the inflation factor in line 51 of 1.15. After 2018, this $1,000 inflated cost will repeat every 5 years, marked with an "x" in 2023 on the attached spread sheet.

I want to project out 30 years.

I can use the formula =IF(F$4=$D37,$E37*F$49,0)
to get to the first occurrence of the expense in 2018, but can't figure out how to repeat it every five years. I am having to manually inflate the costs at the future occurrences and it is both time consuming and fraught with error opportunities.

VERY ELEGANT, The 100+ senior citizens at Ancora Village thank you very much. Seems to work well, issue with 'x' location may be mine!

Thanks again......

Originally Posted by etaf

not very elegant

=IF(F$4<$D5,0,IF(MOD(F$4-$D5,$C5)=0,$E5*F$49,0))

so i'm testing to if the year is less than the expected year and if it is then 0

next I'm seeing if taking the year taken away from the expected year and then dividing by the frequency year is exact ie no remainder
ie
sprinklers
5 , 2018
you expect to pay 2018,2023,2028,2033

2023-2018 =5 divided by 5 =1
2033-2018 =15 divided by 5 =3

and so using the MOD function it tests for no remainder

my figures did not match all your X - i think ... so you may want to check out thoroughly before you use in production