Trouble with Dots Gradient coverage

[sam_sung82]

I'm working on a project that needs a gradient made with dots.
What is giving me a headache is that I need to have the same dot diameter while changing the coverage percentage...

For example, the left side needs to be a 3mm dot at 50% coverage and the right side needs to be 3mm dot at 10% coverage.

Is there a technique or a plugin to do this easily and quickly without doing the math?

Thanks

[Kurt Gold]

Which version of Illustrator are you using?

[sam_sung82]

Sorry, forgot that detail
I'm currently using the CS6 version.