The phrase "about your command of" is correct and usable in written English.
It can be used when discussing someone's proficiency or skill level in a particular subject or language.
Example: "I would like to inquire about your command of the English language during the interview."
Alternatives: "regarding your proficiency in" or "concerning your mastery of".
At the end of day it is all about being in command of your materials, and Cottrell somehow generates highly nuanced and personal work from a process that should not allow it.
But she could face questions about her command of Wall Street arcana.
While Herman Cain's foreign policy stumbles have raised questions about his command of the facts, he says he would consult with military officials and other expert advisers to guide him through the thicket of world affairs.
Mr. Romney's twin victories over Mr. Santorum in Arizona and Michigan have quieted — for now — what had been growing questions about his command of the Republican field and his ability to appeal to the conservative base of his party.
The same was true during the military confrontation in Haiti in 1994, over restoring the exiled president, Jean-Bertrand Aristide, which she favored and drew lessons from about joint command of American armed forces.
Cudicini has built a reputation as an instinctive shot-stopper but there have been concerns about his command of the penalty area, particularly from set pieces, when he has deputised for Cech.
Sometimes it seems that for all of Steiner's vaunted erudition, he is so intellectually ambitious that he frequently feels insecure about his command of the material under review, and so overcompensates with a flustered stream of cultural name-dropping.
Managing Curator of Exhibitions at the museum, Sharon Matt Atkins, talks about the command of the space and its transformational effect.
When a hospital reaches crisis point and stories erupt about patients not being treated, will the commentariat still be gushing about Cameron's command of the centre ground?
He was about to assume command of the unit, and he invited me to the change-of-command ceremony.
