Thank you so much for your help.
I've been using your inputs, and changed my aproach.
This effort comes for the fact that each sheet size has its own border.
Given I cannot tirgger the rule simply by changing sheet size, not even associating a new parameter to the sheet size, I've created a Form, and changed my Rule, based on another discussion I've found on this forum.
Sub Main
If ThisApplication.ActiveDocumentType <> DocumentTypeEnum.kDrawingDocumentObject Then
MsgBox("A Drawing Document must be active for this rule to work. Exiting.",vbOKOnly+vbCritical, "WRONG DOCUMENT TYPE")
Exit Sub
End If
Dim oDDoc As DrawingDocument = ThisApplication.ActiveDocument
Dim oTBDefs As TitleBlockDefinitions = oDDoc.TitleBlockDefinitions
Dim oSheetSizesList As New List(Of String)
oSheetSizesList.AddRange({"A1", "A2", "A3", "A4" })
Dim oChoice As String = InputListBox("Choose Sheet Size.", oSheetSizesList)
MsgBox("You chose " & oChoice, , "")
Dim oChangedSheetSize As Boolean = False
For Each oSheet As Inventor.Sheet In oDDoc.Sheets
'run the Function defined below to update sheet sizes & title blocks
oChangedSheetSize = UpdateSheet(oSheet, oChoice, oTBDefs)
If oChangedSheetSize Then
End If
Next
' Call ChangeStdStyle(oDDoc, oChoice)
' Call UpdateStylesOfExisting(oDDoc, oChoice)
End Sub
Function UpdateSheet(oSht As Inventor.Sheet, oSize As String, oTBDs As TitleBlockDefinitions) As Boolean
Dim oTargetSheetSize As DrawingSheetSizeEnum
Select Case oSize
Case "A1"
oTargetSheetSize = DrawingSheetSizeEnum.kA1DrawingSheetSize
ActiveSheet.Border = "A1"
Case "A2"
oTargetSheetSize = DrawingSheetSizeEnum.kA2DrawingSheetSize
ActiveSheet.Border = "A2"
Case "A3"
oTargetSheetSize = DrawingSheetSizeEnum.kA3DrawingSheetSize
ActiveSheet.Border = "A3"
Case "A4"
oTargetSheetSize = DrawingSheetSizeEnum.kA4DrawingSheetSize
ActiveSheet.Border = "A4"
End Select
Dim oChangedSheetSize As Boolean = False
If oSht.Size <> oTargetSheetSize Then
oSht.Size = oTargetSheetSize
oChangedSheetSize = True
End If
'now deal with changing the title block
Dim oTBDef As TitleBlockDefinition
Dim oTBDefName As String = "FAURECIA"
Try
oTBDef = oTBDs.Item(oTBDefName)
Catch
MsgBox("Couldn't find a Title Block Definition named '" & oTBDefName & "'.", , "")
Return False
Exit Function
End Try
If Not oSht.TitleBlock Is Nothing Then
oSht.TitleBlock.Delete
End If
oSht.AddTitleBlock(oTBDef)
UpdateSheet = oChangedSheetSize
'Atualizar o parametro do tamanho da folha
Dim TamanhoFolha As String
TamanhoFolha = ActiveSheet.Size
iProperties.Value("Custom", "TamanhoFolhaPROP") = ActiveSheet.Size
End Function
Is there a way to automatically close the form right after I selected the sheet size and clicked ok, or right after I load this above window?

Thank you again.