indicate infinite range

[AbelGoodwin1988]

Hello!,
I have two questions.
Excel 2007

	B	C	D	E	F	G	H	I
1	# of Purchases	Food	Cost	Price/Unit	Units	Cost	Price/Unit	Units
2			4/4/2012			4/16/2012
3		Apples, Gala #	2.55	0.78		5.56	0.78

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Grocery Mastersheet​

My wife and I are learning to use some excel and we decided a fun practice might be compiling data with grocery shopping.
One:
What i'm trying to do here is in the column # of purchases help me return the number of times that I have purchased a good.
For example if I made a purchase on 4/4/2012 but not on 4/16/2012 it would be 1. If it was purchased both dates then it would be two.
I'm assuming i'll use something along the lines of COUNTIF. I'm trying to do something like, COUNTIF(C3:AA3,?)/3.
So that question number one.
Two:
I want to, in the units column, have it divide the cost by price/unit to determine the # of units or lbs of something we bought. On some of the cost and price/unit sections though, there is nothing; which returns a div/0 error. I'm assuming i can use an IF formula somehow to say if in these two cells there is a number then divide, if not "".
So, any pointers would be much appreciated!
Man Excel is so fun!
Thank you, again!

 

[Michael M]

You could also have a look here at finding extent of ranges

http://xldynamic.com/source/xld.LastValue.html

 

[Soggy]

I'm not sure you /3 will work. If you have the date then 3 extra cells then it should be divided by 4 shouldn't it.

To count a complete row say 3 you would need =counta(3:3) this will select the whole of row 3 the same as =counta(B:B) would select all of column B. You would need to be careful not to have that formula in that row or column as it would create a circular reference. This is where the cell is in the range that is being calculated so it can't return a result as it relies on the result from itself).

There will bw way to count what you input in the cells underneath so if it's just the date you will have four occurences of the date. You could count the number of items that occur four times.

There is probably a formula to calculate the number of say

 

[AbelGoodwin1988]

Ah, soggy!
B:B would be so useful!, Unfortunately I do want to create the formula in the same row for aesthetics.
I could perhaps create a row above/below each row then put the formula there and then hide it and spread selection to the bottom/top of the two rows?