Well, DDEDIT is the command to edit a dimension.
So depending on what and when you want to do, you could tag that on to
the end of a dimension macro.
Our macros for dimensions look like this (eg linear)
^C^C^P-layer;t;DIMTEXT;m;DIMTEXT;c;14;DIMTEXT;;$M=$(if,$(getvar,tilemode),,vplayer;t;DIMTEXT;;;);;^Pdimlinear^M
This is so that it doesn't matter what layer we are on at the time, we
always get the right layer and colour for our dimtext.
You could always tag on to the end the option to edit, but it might get
annoying if it does it all the time,