Add this to a class that is initialized "With Events". Load the class at startup. Set its Doc property to ThisDrawing.
Code:
Public WithEvents Doc As AcadDocument
Private Sub Doc_BeginDoubleClick(ByVal PickPoint As Variant)
'If item being clicked on is a dimention,
'then open the Mtext editor instead of the properties dialog.
Dim s1 As AcadSelectionSet
Dim oEnt As AcadEntity
Set s1 = ThisDrawing.PickfirstSelectionSet
If s1.Count > 0 Then
For Each oEnt In s1
Select Case oEnt.ObjectName
Case Is = "AcDbAlignedDimension"
ThisDrawing.SendCommand "ddedit "
Case Is = "AcDb2LineAngularDimension"
ThisDrawing.SendCommand "ddedit "
Case Is = "AcDb3PointAngularDimension"
ThisDrawing.SendCommand "ddedit "
Case Is = "AcDbDiametricDimension"
ThisDrawing.SendCommand "ddedit "
Case Is = "AcDbOrdinateDimension"
ThisDrawing.SendCommand "ddedit "
Case Is = "AcDbRadialDimension"
ThisDrawing.SendCommand "ddedit "
Case Is = "AcDbRotatedDimension"
ThisDrawing.SendCommand "ddedit "
End Select
Next oEnt
Else
End If
End Sub