Sound fade partially

[AridanosYT]

Hi, wonder if anyone can help me with that question. I know I can control the volume, made it fade in and out, but I want to know if it's possible to partially fade sound in and out. For an example, at the beginning of the clip, the sound is at 100%, but fade to 30% when a character talk, then I bring it back to 100% when the character is done talking. Or do I need to do this outside of SFM. Thanks in advance.