Subtracting data for specific period of time

I have a table set up (based on an the old EXCEL spreadsheet we used prior to
this)and I would like to be able to have the total gallons used calculated
from the beginning of a particular period to the end, by subtracting the
starting H20Meter reading by the ending H20 Meter reading. This is how my
table is set up:

GWID-autonumber
Date - Date/Time
Employee, Text
H20MeterReading - Number, long
GPM - Number, long
24HRGAL-Number, long

Is the query or report the place to do this. Please let me know what I need
to do to fix this if I am wrong, etc. I am a newbie so please be gentle.
Thanks

Yes, it's certainly possible to do this - just before we start. though, it's
not a good idea to call a Date field "Date" - although Access copes with it
in most situations, sometimes it doesn't. It's also a bit confusing - it's
much better to call the field "ReadingDate" or something more descriptive.

OK, so what you're after is the latest reading minus the earliest reading
within a given date period, yes? Or are you looking for the meter reading
immediately before the beginning of your period (which is considerably harder)
.. Also, does GPM identify each meter?


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Answered in one of the other threads where you posted this q.

Thank you for your reply and suggestion. Yes, I am looking for the meter
reading at the beginning of a particular period, say August 1st and the
difference at the date I put in for the end, say August 31. I planned on
writing a query whereby I would put the range of dates and the calculation
would be made from the dates I put in.

"David S via AccessMonster.com" wrote:

Yes, it's certainly possible to do this - just before we start. though, it's
not a good idea to call a Date field "Date" - although Access copes with it
in most situations, sometimes it doesn't. It's also a bit confusing - it's
much better to call the field "ReadingDate" or something more descriptive.

OK, so what you're after is the latest reading minus the earliest reading
within a given date period, yes? Or are you looking for the meter reading
immediately before the beginning of your period (which is considerably harder)
.. Also, does GPM identify each meter?


--
Message posted via AccessMonster.com
http://www.accessmonster.com/Uwe/For...eries/200510/1