adding to item properties

[Legacy_Jerrus]

               

Ok, I know how to add an item property such as +1 attack bonus, but how do I increase an item property? For example: If I want a black smith to be able to increase the attack bonus of a any weapon by 1 even if that weapon already has an attack bonus.

               
               

               
            

[Legacy_HipMaestro]

               

x2_inc_ws_smith.nss in the standard resources has a forge system that does that much.