Sub update_cell_data()

     NewCellValue = "test data"  ' new value to insert into the cell below
    CellID = "Cell_ID[2, 2]"
    
    ' temporarily turn on hidden text
    ActiveDocument.ActiveWindow.View.ShowHiddenText = True
    
    Dim Rng As Range, aTable As Table, r As Long, c As Long, CellText As String, FoundText as Boolean
     For Each aTable In ActiveDocument.Tables
        With aTable
            For r = 1 To .Rows.Count
                For c = 1 To .Columns.Count
                    CellText = .Cell(r, c).Range.Text
                    FoundText = InStr(CellText, CellID)
                    If FoundText Then
                        MsgBox "here"
                        .Cell(r, c).Range.Text = NewCellValue
                    End If
                Next
            Next
        End With
    Next aTable
    
    ' turn off hidden text
    ActiveDocument.ActiveWindow.View.ShowHiddenText = False
End Sub