hi all hope everyones good

i need some help with a project of mine and hoping this forum would be
able to find it here for a gas bill calculator

my spread sheet needs to do this.

i want to place the this information as input.

2 dates a from and to date
2 readings( from meter)
a specific number relating to the relevant area and charges
a slot for if the meter is metric or imperial

process

i want the spreadsheet to calulate Kwh from the readings which i know
how to do already.

this is the part i need help with once the Kwh has been calculated i
need to calculate depending on what months it covers with this

Jan 28.46kwh per day
Feb 31.51 Kwh Per day
mar 8.76 kwh per day
april 9.04 kwh per day
may  1.47 kwh per day
june 1.58 kwh per day
july 1.47 kwh per day
august 1.47 kwh per day
sep 1.52 kwh per day
oct 8.75 keh per day
nov 29.41 kwh per day
dec 28.41 Kwh per day

so say the bill ran from 13/01/08 - 13/03/08 i would need 1 part to
calculate the unit over that period so 18 days of jan 28 feb 13 mar and
then multiply the outcome by x amount providing the total units are
under the total units used.

then the final phase would be to calculate how many units are not
accounted for and bill them ay Y ammount

then show the combined ammount and include vat at 5%

please help