Great! I'm still not sure how I would create the Grain datablock. I would have it inherit the default values assigned to the Item datablock. Maybe the types would look like this:
Type Item
Field Class:String="Item"
Field Layer:Int=18
Field UseMouseEvents:Int=1
Field Size:Int=5
End Type
Type Grain:Item
Field ItemType:Int=0
Field Attack:Int=0
Field Price:Int=2
End Type
Local Grain = New Item
Type Item
Field Class:String="Item"
Field Layer:Int=18
Field UseMouseEvents:Int=1
Field Size:Int=5
End Type
Type Grain:Item
Field ItemType:Int=0
Field Attack:Int=0
Field Price:Int=2
End Type
Local Grain = New Item