Populate chart with data from column (Unknown number of rows)

Im not sure how to do this, I want to populate a simple bar chart with data from specific columns and specified criteria.
Example:
All cells in a column with "A" for one set of data
All cells in a column with "B" for one set of data
All cells in a column with "C" for one set of data

All in the same chart via VBA

Any hints tips or examples are appreciated.

P.S.
Can a mod please move this to the Charts forum (oops)

Can you post an example of what you mean?

It sounds like you have a column that can have A, B, or C, and you want to select data in some other column in three different series depending on whether the column has A, B, or C.

But you can see that I have to do some guessing to come to that conclusion--you don't describe the data; where it is; or whether you in fact want multiple series, or just three bars in a single series.

I thought I could get a general idea in my original post...Oops...

On worksheet "Calibration Log" is the data in column "L".
I want to graph all past due (negative values)
All the values that are 10 days out and 30 days out. (Positive values)
I know how to change colors and such just not how I can populate the chart on worksheet "Val-Cal_Due" via VBA, the idea is to have the chart update when ever the sheet is active.