Select Block based on Block Handle ID
If you know the Handle value of the target entities, you can call AcadDocument.HandleToObject([handle]). Note, you'd want to have proper exception handling code, in case the entity that had the handle previously has been erased prior to your code runs. In your case, the code would look like:
Private Function UpdateBlockReference (handleValue As String) As Boolean
Dim obj As AcadObject
Dim blk As AcadBlockReference
On Error Go BAD_HANDLE
Set obj=ThisDrawing.HandleToObject(handleValue)
If TypeOf obj Is AcadBlockReference Then
Set blk=obj
If UCase(blk.EffectiveName)="MY_TARGET_BLOCK" Then
'' Update this block reference
End If
End If
UpdateBlockReference = True
Exit Function
BAD_HANDLE:
'' MsgBox "Invalid handle found!"
UpdateBlockReference = False
End Function
You did not say, but I'd guess your code run in Excel's VBA, right?
If so, of course "ThisDrawing" is not valid in Excel VBA.
You need to replace it with the variable referring to an opened AcadDocument object.
For example, in your Excel VBA, you might have this kind of code to connect to AutoCAD and open a drawing:
Dim cadApp As AcadApplication
Dim dwg As AcadDocumen
Set cadApp=New AutoCAD.Application
Set dwg=cadApp.Documents.Open ("....file path/name...)
...
Then you can use "dwg" to replace "ThisDrawing" in my code sample.
Firstly, it is hardly a good workflow to automate a complicated desktop app, such as AutoCAD from another application (Excel app in your case): user unnecessarily has to face 2 applications for a task.
Anyway, in your Excel VBA side, if you want to update a given drawing, the usual process is to first try to find a running AutoCAD session. If found, check if the target drawing is open in AutoCAD session or not. If found, do something with the drawing. If the drawing if not found open, open it in AutoCAD. If there is no AutoCAD session, start one and then open the drawing.
The VBA code should look like something as following:
Dim cadApp As AcadApplication
Dim dwg As AcadDocument
Dim targetDwg As AcadDocument
On Error Resume Next
Set cadApp=GetObject(, "AutoCAD.Application")
if cadApp Is Nothing Then
Set cadApp = CreateObject("AutoCAD.Application)
If cadApp Is Nothing Then
MsgBox "Cannot start AutoCAD!"
Exit Sub[Function]
End If
Else
For Each dwg In cadApp.Documents
If UCase(dwg.Name) = "C:\MYFOLDER\MYDWG.DWG" Then
Set TargetDwg=dwg
Exit For
End If
Next
End If
If targetDwg Is Nothing Then
Set targetDwg=cadApp.Documents.Open("C:\MYFOLDER\MYDWG.DWG")
End If
'' Now you have the running AutoCAD session and the target drawing
It would be better for you to provide more detailed context in which "unique name" means. But let me make assumption. Say, you have a block called "WorkStation", and you insert 3 block references of of this block into drawing. Naturally, all 3 block references have name "WorkStation" shown in the Properties window. But you want give each block reference its own name, like "WorkStation 1" or "WorkStation 2" or "WorkStation 3", or simply "#1", "#2", or "#3". This extra piece of data can be either visible in drawing as required, or not visible but accessible programmatically (by code) for business reason.
If that is the case, AutoCAD's way of using block has already provide this functionality since its beginning of near 40 years ago: using Attribute within block. Add an attribute to the block with whatever tag you like, such as "Unique Name", "Station Number", or even "Name", and give the attribute a different value in different block reference. It the attribute is not meant for being visible and only accessed/controlled by programming code (to enforce the uniqueness, for example), you can flag the attribute as "Invisible". Also, besides Attribute, you can also attach data with unique value to block reference (and any type of entity, for that matter) as XData or ExtensionDictionary through your code.
But I'd think, in most cases, attribute is what you are to use, simple, easy and basic for every CAD user.
