How to call variable in Graph code (in Y1Axis)

Hello,

I know it is possible to change to scale of a graphic with the following code :

 <Y1Axis axisMinAutoScaled="false" axisMinValue="5000" axisMaxAutoScaled="true" majorTickStepAutomatic="false" majorTickStep="1000">
    ...
</Y1Axis>

But I want to have the axisMinValue determined DYNAMICALLY based either on a variable, or on an element from my input XML .

In my rtf document, I have defined a xdoxslt variable ( <?xdoxslt:set_variable($_XDOCTX, ‘V_MIN’, 10000)?> ).

How can I call this variable in the value for axisMinValue?

If not feasible, can I call an element from my xml?

Thanks in advance for any clue that could help.

Regards,

Alexia