[Freesurfer] White matter volume of a costumized Gyrus

Dear Freesurfer team,

I am working with calculated volumes of a gyrus (a costumized label).

I currently use mris_anatomical_stats to calculate the volumes of my gyrus (in label format).

According to the freesurfer tutorial (as I understood), one of the stats outputted from mris_anatomical_stats is the volume of the gray matter surrounding the white/gray matter border (a surface) specified by the inputted label.

We are actually interested in the white matter volume (instead of gray matter volume) inside this ROI (a gyrus in our case) specified by the label.

I didn't find yet a command in freesurfer from where I can extract the white matter volume of a gyrus from a costumized label.

Could someone advise me?

Best regards,

Josue