Get The Last Three Non Blank Cell In A Column

I have a data in a column B, from B17 to B1000. the data looks like:

0.1
0.5
20
15
16
20
10

I want to get the last non-blank cell (in the previous example = 10), and the one before it (20), and the one before it (16).I mean I want the last three non-blank cells. I used =INDEX(B17:B1017,MATCH(9.99999999999999E+307,B17:B1017)) to bring the last non-blank cell. I'm using excel 2003, but it's OK to use Excel 2007 if it will solve the problem.