No they can't. Variable ND filters are used to slow down the exposure when you need a slower shutter speed than the combination of exposure parameters and light will allow - examples are to render a waterfall that is silky or to get a shallow DOF in bright conditions, or in the video world to get your exposure to 1/60s or whatever 1/(2 x Frame rate) is. How do you do that in post?
That said, variable ND's can leave some weird cross polarization artifacts especially on wide angle lenses as you dial up the strength. Personally I much prefer carrying a 6 stop and 10 stop pure ND filter rather than a variable as the results are much more predictable.
BTW, Cokin makes screw on variable ND's that you should be able to get in Europe - also B&W and Heliopan - all European filters.