The formula to jump to a random slide between Lowest Slide and Highest Slide is: (I think!)

Int((highest slideNo - one less that lowest slide number)*rnd) + lowest slide number
So to jump to a slide between 73 and 93

Int((21)*rnd) +73

rnd is always between 0 and 1 (can be 0 but never 1)

Int(21* rnd) is 0 to 20

Add 73 gives 73 to 93