I'm not sure I get where you're coming from. Is this a 'one off' edit that you need to do? If so, then you spent a whole lot more time posting your query to this forum than it would take to do the workaround I posted. If not, and in fact you frequently need to modify the same dimension within the same dynamic block, then that can indeed be done. What I have done in that situation in the past is to do a text override on the dimension so that it contains just a space. Then add an attribute that displays the same text style and size as the dim text, and add a field to it referencing the dimension value. It will display the dim value unless you need to customize it and in that case, you are just editing the attribute.