Just make the file path this way:
AppPath & "hit" & 1+random(3) & ".mp3"
If it doesn't work for, change the number to a string this way:
AppPath & "hit" & str(1+random(3)) & ".mp3"
Random() is zero indexed, so random(3) returns 0, 1 or 2. That's why it's 1+random(3), since your hit sounds don't start from 0.