Dear goh6613,
Put the toolbar items needed to be disabled into this Editor.DisableItemList string.
For example:
<CE:Editor id="Editor1"
DisableItemList="Bold, Italic" runat="server"></CE:Editor>
C#:
Editor1.DisableItemList = "Bold, Italic";
VB:
Editor1.DisableItemList = "Bold, Italic"
Regards,
Eric