TO Split the source fileld in two target Nodes if the length of the source field is greater than 20,

HI All ,

I have a requirement that from idoc  we will get 1 field . if that field length is suppose 35 then my target filed should split in to 2 nodes , in that 1 filed should contain till 20 length & remaining 15 to another node.

if the source filed " ITEM_NAME" has a length more that 20 ,  then the first 20 length should create a node "Line_B1"  in that the item name field will be having the first 20 characters & the second Node "Line_B1" to be generated and in that the item name filed will be having the rest 15 characters.

please provide the solution for this, as I had struck here from many days.

hope I will get answers.

Thanks in advance.