I could do with some help on a tricky issue I'm having with graphing please!

I've written a spreadsheet to help me produce a report for an exercise test. I then import a set of raw data that the spreadsheet manipulates to produce graphs etc for the report.

One of the values the spreadsheet calculates is the time that exercise finishes. The raw data proceeds past this point, and I want to plot some of the graphs only up to the time that exercise finishes. The columns from the raw data are always the same, but obviously everyone will finish exercise at a different time point (Row).

So, what I want to do is plot my graph, only up to a particular time point (row), based on the cell reference that the spreadsheet has already calculated.

What I hoped would work is that I could just incorporate that cell reference into the Chart Series data range, something like:

Series X Values
='Raw Data'!$L$3:$L[Lookup Tables!L11]
Series Y Values
='Raw Data'!$M$3:$M$[Lookup Tables!L11]

.....but I can't get it to work! :-(

I've looked at dynamic chart ranges etc, but that doesn't seem to fit with what I want to achieve.

I'm hoping it's just a case of getting the syntax right!?

Can anyone help please...... Thanks!!!