reorganising large amounts of excel data

Hi
i have a question regarding reorganisation of data in excel. I'm working on a geological stratigraphy project and have an excel dataset of a large number of rock layer thicknesses (in stratigraphical order). For further analysis I need to rearrange the data so that instead of each excel row corresponding to one rock layer with the thickness mentioned in the cell, each row corresponds to 1cm of rock, and in each cell the rock type is mentioned. So for example:
3cm limestone
1cm marl
2cm limestone

would become:
1cm limestone
2cm limestone
3cm limestone
4cm marl
5cm limestone
6cm limestone

Is there any way to have excel automise this (since it will take really long to do manually)? Or any suggestions on how to handle such a task? Thank you!
Max

Thanks for the reference Søren Larsen! I'll try it out!

Spencer101, it is about 20m of rock, and every row is 1mm, so 20 000 rows.

I checked it out, and the solution doesn't quite work in my case; i would use 'lookup' to look up the lithology instead of a pagenumber. Also the pagenumbers in the pdf example are non repetetive (just 1, 2, 3, etc.), and my lithologies and thicknesses do repeat, so it wouldn't help to look up a string like 'limestone'.
Any suggestions?

no, because i need them to remain in the order they are in. I've had a little progress; my spreadsheet now looks like this:
A B C D E
Thickness Cumulative thickness Lithology MM from base Lookup function
0 0 0 0
1 1 Limestone 1 0
3 4 Marl 2 4
2 6 Limestone 3 4
4 4
5 6
6 6
...etc
(i hope it's clear). So what i need now is a way to get an f column filled with the lithology, so that if in column e there is the value 0, it will display limestone, if 4 marl, and if 6 limestone again, etc. I was thinking of a repetetive if then function, but im not sure how to do this.
thanks!

Hell yeah it does work! This will surely help me a bunch.
You have earned a place in the acknowledgments :D.