While you're on your feet ...

My extreme dislike of this expression dates from my childhood when, as an only child, I lived in a non-centrally heated house with my parents.  On a winter's evening we would be sitting round the fire, dreading having to go out into the icy rooms beyond. If a call of nature happened and the unfortunate victim (usually me!) stood up to go to the bathroom, my mother or father would say: "While you're on your feet, could you make a pot of tea, bring some coal in, stoke the fire, lay the table for breakfast tomorrow and put hot water bottles in all the beds?" Consequently we sat there, crossing our legs with increasing rigidity, until one of us gave in and dashed out shouting, "I can't wait!"  This was merely a temporary remission as, on return, there would be the lugubrious refrain: "While you're ..."