The simplest method of adding additional blocks/group of cells when the previous ones fill up is to create a custom quick part consisting of a complete block/group and insert that.
As for changing colours when a checkbox is checked, you can add the following code to your document's 'ThisDocument' code module:
Code:
Private Sub Document_ContentControlOnExit(ByVal ContentControl As ContentControl, Cancel As Boolean)
Dim Rng As Range
With ContentControl
If .Type <> wdContentControlCheckBox Then Exit Sub
With .Range
If .Information(wdWithInTable) = False Then Exit Sub
If .Rows(1).Cells.Count = .Cells(1).ColumnIndex Then Exit Sub
If ContentControl.Checked = True Then
.Rows(1).Cells(.Cells(1).ColumnIndex + 1).Range.Font.Color = wdColorRed
Else
.Rows(1).Cells(.Cells(1).ColumnIndex + 1).Range.Font.Color = wdColorAutomatic
End If
End With
End With
End Sub
For installation instructions, see:
http://www.gmayor.com/installing_macro.htm
Note: You will need to re-save your document in the .docm format to retain the macro.