Thanks for your help, I solved the problem with the following peace of code in the oledragdrop.

It was simple in the end, instead of trying to tell AddListItem when I wanted the Item to reside I allowed the method to dictate it location then using the property NewItemId I was able to reference the new items location and update the additonal columns.

LPARAMETERS oDataObject, nEffect, nButton, nShift, nXCoord, nYCoord
LOCAL aValues[1]

IF oDataObject.GetFormat("VFP Source Object")
WITH oDataObject.GetData("VFP Source Object")
IF .Name = THIS.Name &&don't allow dragdrop on self
RETURN
ENDIF
ENDWITH
ENDIF
IF oDataObject.GetFormat("OLE Variant Array")
oDataObject.GetData("OLE Variant Array",@aValues)
IF (This.AddSupplier(aValues[1,3]))
This.AddListItem(aValues[1,1])
This.AddListItem(aValues[1,2], This.NewItemId , 2)
This.AddListItem(aValues[1,3], This.NewItemId , 3)
nEffect = 1
ENDIF
ENDIF