You can create a formula that calculates the number of lines required for the description field - if your print area is 40 characters and the description is 90 characters then the value would be 3 - add this to a stored variable for each record to get line count. You would then go to the next page when that number exceeds a certain amount.
The only other issue would be fixed vs. variable fonts as was mentioned - if you use variable fonts then you would have to figure the worst case width (least number of characters that fill the space) in which case you would occasionally use more lines than needed
Hope this helps,
Cyber-guys