Need Excel help

[Strider]

I have a spreadsheet that looks a bit like this:

A B C
1 1 12
2 2 30
3 3
4 4
5 5 45
6 7 23
7 9
8 10 11
9 17
10 22 33
11 25 35

In column C, I need to calculate: the last value in B minus the current value of B divided by the current value of A minus the previous value of A all times 1000.

For example, here's the formula I used in C2: (B1-B2)/(A2-A1)*1000

Problem is, I can't just use the fill handle to fill in the cells because it'll count the blanks as 'zero'. I need it to use the next value in column B, for example (B5-B2)/(A2-A5)*1000.

How can I do this without going thru each individually? I tried using autofilter to filter out the blanks in column B, then filling the formula, but that didn't work.

Thanks in advance

[Phats]

um, I'm not quite sure I understand you correctly but if you want to keep the B2 and the A1 cells constant then you can use a $ sign before each one, then when you copy and paste the formula, the number and letter will stay the same while the rest change accordingly, remember to put a dollar sign in front of each letter or number like this $A$1 that you want to stay constant, hope this helps.