[MAYA] MRampAttribute in a context

Hi guys,

I’ve coded a tool (mpxcontext) and its related GUI (for tool properties panel)
I have multiple controls now (checkboxes, sliders and a few other things) that can communicate with the tool via the flags.
everything works fine, but I’m now stuck on a feature:

In the tool properties panel, I’ve added a editable curve (ramp) that works the same way as the other controls (its callback send a string to the mpxcontext). but my problem is that I don’t know how to use the ramp’s interpolated data in my mpxcontext.

in the mpxcontext I’ve created a MRampAttribute object that I want to initialize with a string containing all the points of the curve. My problem is that when I call the addEntries function, it returns a MStatus::kfailure.
It seems that I can’t instanciate an arbitrary MRampAttribute object and fill it by myself.

to see an example of what I want to do, look at the soft selection tool in maya: It has a ramp that can pass data to the selection tool.

Does anyone know how to do that?

thanks