Theese 3 formats are described as Private for VFP in FoxPro.H so You can't use them in ActiveX

*-- Clipboard formats (Private to VFP)
#DEFINE CFSTR_OLEVARIANTARRAY "OLE Variant Array"       && VFP array
#DEFINE CFSTR_OLEVARIANT      "OLE Variant"             && Data in variant form
#DEFINE CFSTR_VFPSOURCEOBJECT "VFP Source Object"       && A reference to the VFP source object

But There is a workaround. In OLEStarDrag in TreeView Control:

LPARAMETERS Data, allowedeffects
c_str = "" 
FOR asd = 1 TO 9
    c_str = c_str + subs(THIS.SELECTEDITEM.TEXT, 1, 3)+CHR(13)
NEXT
c_str = LEFT(c_str,LEN(c_str)-1)
Data.SetData(c_str, 1)  && Text

in OLEDragDrop in VFP Control (ListBox)

LPARAMETERS oDataObject, nEffect, nButton, nShift, nXCoord, nYCoord
IF oDataObject.GetFormat(1)
   m1 = ALINES(aData1,oDataObject.GetData(1),.t.,CHR(13))
   FOR asd = 1 TO m1
       this.AddItem(aData1[asd])
   NEXT
ENDIF