yup yup. I do that shit all the time. Matter fact, i think the plants benefit from being exposed to both spectrums during flowering. Thats why some people prefer to go with a dual arc lamp during the entire grow, as opposed to MH for veg and HPS during flowering.
For me, in the morning i bring my two WW sativas down into my grow tent, from up in my top cab where i have shitloads of CFLs, down into my growtent where i have a crop already flowering under a 600w HPS bulb. At night when the dark photoperiod comes, i take the WWs n put them back up in their home, so i dont interrupt the constant photoperiod. Your fine bro, if anything your plants will benefit from the extra spectrum exposure.
UNLESS
your using way weak amounts of CFLs and then you put the plants underneath something DRASTICALLY stronger. Like say your using 3 45w CFLs, and then you take your plants n throw them under a 1000w HPS bulb. That might shock the plants a little bit n slow down growth. But if your not making too too much of a drastic change, then your golden like gloves buddy