This may be VERY old, but VB is still BASIC so here goes:
The command RND, or in VB 'RANDOM' basically generates you a number between 0 and 1.
RND(1) - Generate a number between 0 and 1
*8 - Times it by 8 (this is our max or 'ceiling')
+1 - Means, keep the number equal to or above 1
Then if you do:
This does all of the above, but keeps the number as an integer (ie 4 instead of 3.5, or 4.5 etc)
So if you need an 8 digit random number.
INT(RND(1)*99999999+1) - should do the trick