How to apply modifications only to selected clip range

I have imported some video from an old VHS camcorder. I wanted to edit only certain sections of the clip with the colour change tools as it appears I can by positioning the handlebars of the range selector in the timeline window. However, every time I select or try a particular modification, it changes the whole clip and not just the frames I appear to have selected. Is this the only option in iMovie? Thank you.