[DerekAsirvadem]

You are working at the level of using one tool to produce a result, and then another tool to change/improve the result. Several options, depending on whether you are Unix-centric or MS-centric.

1 Why don't you use one tool to do the entire job, and automate the whole process (eliminate the manual labour entirely, each time [month ?] you need to create the charts. Have a look at GNUPlot, etc. Just feed it a file (data series) and a bunch of chart parameters, and it ...

2 You might also look into Numbers (on the Mac, since you have one for OG) as opposed to Excel (on the piece of c#@p); it is a lot easier to create great looking charts, directly from a .CSV file that contains data series; then mess with the graphics.

3 OGS may well do the job but I have not used it.

In both instances, I am asking you to remove yourself from your question, which has limited solutions built into it, and look at only the problem:
• you have a data series sitting in a file somewhere
• which you do not need to translate
• you want to erect a chart (a good looking one)
• you want to do that frequently
• you want to vary the charts
then choose the tool with awareness of the capabilities and limitations of each; whether you can reasonably use it for the entire task, or whether you have to use a sequence of tools.
Cheers