Multiple Caster Level Progression Prestige Classes

[Fixer]

...do you want Homebrew?

I don't think that would be as helpful. If people are willing to homebrew they don't need official sources and such. If there is enough demand for it I'll create a new table for homebrews but we will see.

Green Whisperer gives +5/+5 spellcasting progression.

How many levels does it have? Please?