The fouth clause can be set to TRUE to do a nice range lookup, I use this a lot for DnD type tables:
Table
1 TextA
3 TextB
6 TextC
9 TextD
A1= ROUND((RAND() * 9)+1,0) <generate random number 1-10>
A2= VLOOKUP(A1,Table,2,TRUE) <Returns TextX based on probability in first row of table>...