Shirley, (Eugene, OR)
Second, be sure you have enough tension on the awning torsion spring assembly. A properly tensioned spring should require a bit of effort to extend the awning during normal set-up. Of course, driving down the road, if the wind gets under the canopy, it will be easily extended if the locking mechanism is non-functioning. You didn't mention what brand awning you have, but the number of turns on the spring assembly is determined by the length of the awning. The manufacturer will have a chart you can refer to for the number of turns required by your awning.
And thirdly, in addition to properly securing the awning lock mechanism, I also recommend a product called Awning Cinch Straps. One of these little straps on each awning arm should prevent the arms from jumping out of position and falling away from the RV and prohibiting the wind to inflate the canopy and extend the awning further.