We sell valves for oil and gas pipelines and installations. We use one short description for sales orders and then very long detailed descriptions for purchase orders on how the valves are to be built. As Sage 100 only has one item description field we came up with the following solution.  

In CI_Item I created a UDF called Purchase Order Notes that is the same size as the Extended description field, 4096.  I then placed it on the second tab where this is a large blank space across from the four (4) built in UDFs.  This would hold the second description. Then in Purchase Order I created a script and attached it to the item number field. See below.  When an item is entered the Purchase Order Notes is it is written to the ItemCodeDescription field. The business frame works takes care of writing it out to the CI_ExtendedDescription table. 

retVal=0
itmCode=""
oItmSvc=0
Notes=""
Desc=""

retVal=oBusObj.GetValue("ItemCode$",itmCode)
retVal=oBusObj.GetValue("ItemCodeDesc$",Desc)
oItmSvc = oBusObj.GetChildHandle("ItemCode")
set oItmSvc=oSession.AsObject(oItmSvc)
retVal=oItmSvc.Find(itmCode)
retVal=oItmSvc.GetValue("UDF_PURCHASE_ORDER_NOTES$",Notes)
If Notes <>"" Then retVal=oBusObj.SetValue("ItemCodeDesc$",Notes)