data validation and predict future costs

Hi

ive got a forecast spreadsheet and ive used simple formulas to predict future expenses for the next two years.

i need to be able to predict future costs quicker instead of changing formulas per line item.

i've completed 2018 & 2019 costs as per example as what i would like it to look like however not all cost categories use the same rates - see rates tab.

i would like to use different rates as in columns M&N in rates tab as well as different averages to predict future costs (see columns D thru G in rates tab as well)

and i've got a one-off cost in 2018 for global meeting that i need to forecast in Jan only - i assuming to simply add that value to Jan

does anybody know of data validation formula to simply change the values for future expenses more quicker instead of changing formulas per line item?

thanks

wasn't sure if the other thread had been posted - it's been marked as solved

hope it help.

highlight orange is what i change.

yellow is the one off.

BoredWorker this is great thanks. could you please explain what do numbers in column J in rates tab represent.

The column J represent the col_index_num in vlookup

The year 2018 need the column 3, 2019 need column 5 and etc.

Jus want to know.... did the first 3 month average hv any used?

Hi BoredWorker, Glenn,
both of your versions have worked for me.
thank you very much for your help.