Crystal* Formula help please

I have a crystal report where I group by case number.
The idea is to print a message beneath each group if there is a carton#

Packing note print after every case the following;
Qty Description Weight
5 External Modems .3
7 Keyboards .2
6 Harddrives 1
All above packed into Carton# 1

4 Motherboards .4
3 Internal Modems .2
6 Boxes CD-R 1

All above packed into Carton# 2

The above is fine but if items are not packed into a carton then the following still prints but without the carton #

2 Monitors 5.3
1 HP Printer .9
All above packed into Carton#

How do I adapt my formula not the print the message if the Carton# fileld is empty?

My formula currently is:
"All above packed into Carton# " & {Details.caseno}

Suppose should be some thing like:

"All above packed into Carton# " & {Details.caseno} where {Details.CaseNo} > ""

Code:

---

if isnull({Details.caseno}) then

""
else

"All above packed into Carton# " & {Details.caseno}

---

or something similar. It also might be

Code:

---

if isnull({Details.caseno}) or {Details.caseno} = 0 then
""
else

"All above packed into Carton# " & {Details.caseno}

---

depending on that the field contains.

HTH