I want to create a formula showing me the days in a certain time period and multiplying that by a price.

Question

I am creating a spreadsheet with renting prices for each month. and need help on the formula below.
Basically, I want to add up a total base rate for the nights people are staying. Can you please help me out with this?

Answer 1

Hi Caleb
Well, to begin with, if John checked out on December 1, he didn't stay any nights in November.
The formula is is bit involved due to the rate change. The version below handles this with a pair of IF statements that check to see if check in and check out occur in the same month.
If not, the first calculates the charges for the number of nights stayed in the check in month, and the second calculates the charges for the number of days stayed in the check out month. (E2)
If check in and check out occur in the same month, then the first calculates the charges for that month, and the second returns a null string ( "" ). (F2)
The results of these calculations, and the fixed booking fee (included in the formula, not gathered from Table 1), are summed in the next cell. (G2)
Formulas:
All are in Table 2, and are filled down their respective columns after being entered in the indicated cell.
E2: =IF(MOD(MONTH(D2)-MONTH(C2),12)=0,DATEDIF(C2,D2,"D")*VLOOKUP("unit "&B2,Table 1 :: $A:$N,MONTH(C2)+2,),DATEDIF(C2,EOMONTH(C2,0)+1,"D")*VLOOKUP("unit "&B2,Table 1 :: $A:$N,MONTH(C2)+2,))
F2: =IF(MOD(MONTH(D2)-MONTH(C2),12)=0,"",DATEDIF(EOMONTH(C2,0)+1,D2,"D")*VLOOKUP("u nit "&B2,Table 1 :: $A:$N,MONTH(D2)+2,))
G2: =SUM(E2,F2,60)
Note:In the present form, the formulas will correctly handle checkin/checkout dates in the same month or in two consecutive months (eg. November/December, December/January, etc.) but are not capable of determining the correct date for the rate change where the stay extends across two month ends.
The formulas could be combined by substituting the first and second (without their = signs) into the third, replacing "E2" and "F2" respectively. Writing them in that form originally makes for more chances to make an error, and makes the whole formula more difficult to read.
Details on each of the functions used may be found in the iWork Formulas and Functions User Guide, which you may download via the Help menu in Numbers '09.
Regards,
Barry