The SendCommand method is asynchronous. It runs after you vba code finishes. You need to use the vba api to import a block and insert it. For example, below is how I insert a titleblock at 0,0 where strFileName is the path to the block.
'InsertTB:
Dim dInsert(0 To 2) As Double
dInsert(0) = 0#: dInsert(1) = 0#: dInsert(2) = 0#
Set oTbNew = ThisDrawing.PaperSpace.InsertBlock(dInsert, strDest & strFileName, 1, 1, 1, 0)
'put tb on specific layer
Set oNewLay = ThisDrawing.Layers.Add("TITLEBLK")
oTbNew.Layer = oNewLay.Name