I'd have to agree with radar rambler, to achieve a CDA the aircraft have to be reduced to 220kts. (isn't that in the definition somewhere?)
I've tried to get pilots to do a CDA at high speed and they almost always make a mess of it. It's all very well to say that's the pilot's problem but when it came to night time KPIs that excuse didn't wasn't accepted and the edict was reduce them to 220kts first, even if they're number 1.