I am having trouble understanding this sentence from Living Latin: A Graded Reader:
Pro isto vestro in me officio pares agere gratias vix possum, referre nequaquam!
I guess it means something like
I can hardly thank you enough for this favor you have done for me, let alone repay it!
But I can't parse the grammar of the first part of the sentence, "in me officio" is "for me", but "pares" and "vestro" sound out of place to me. I am surprised there is no relative clause.