Simple way to achieve this is:
Option Explicit
Sub GetSomeBrackets()
Dim doc As Document, par As Paragraph, rng As Range
Dim bPos As Long, ePos As Long, sText As String
Set doc = ThisDocument
For Each par In doc.Paragraphs
sText = par.Range.Text
bPos = InStr(1, sText, "[")
ePos = InStr(bPos + 1, sText, "]")
If bPos > 0 And ePos > 0 Then
Set rng = par.Range
rng.MoveStart Unit:=wdCharacter, Count:=bPos - 1
rng.End = rng.Characters(Int(ePos - bPos) + 1).End
rng.Select
rng.Bold = True
MsgBox rng.Text, vbInformation, Len(rng.Text)
Set rng = Nothing
End If
Next
Set doc = Nothing
Set par = Nothing
End Sub