You need to loop through entities in the block definition(AcadBlock) to find the entity in interest, and its position to the block's base point (0,0,0). Then for each of the block references, factor in the block refernece's insertion point.
The pseudo code would look like:
'' Get the position of the Solid inside the block definition
Dim blk as AcadBlock
set blk=ThisDrawing.Blocks("myBlock")
Dim ent as AcadEntity
Dim position(0 to 2) As Double
For Each ent in blk
If TypeOf ent Is AcadSolid And [some other condition to make sure it is the target, if necessary] Then
position=[Get a set of coordinate from the Solid, such as one of its corner...]
Exit For
End If
Next
'' Get the positions related to the drawing's 0, 0,0 (such as ModelSpace's World Origin:
Dim bref As AcadBlockReference
Dim pos() As Variant
Dim i As Ineter
For Each ent in ThisDrawing.ModelSpace
If TypeOf ent Is AcadBlockrefernece Then
Set bref=ent
If UCase(bref.EffectiveName)=UCase("myBlock") Then
ReDim pos(i)
pos(i)(0)=bref.InsertionPoint(0) + position(0)
pos(i)(1)=bref.InsertionPoint(1) + position(1)
pos(i)(2)=bref.InsertionPoint(2) + position(2)
i=i+1
End if
End if
Next