first create your vport. from paper space double click inside the vport so you are in floating model space and type the following.
z (return)
s (return)
1/50xp (return)
the 50 above is an example of a scale, and it can be changed obviosuly to whatever scale you require. after doing this you should use the pan command to locate your drawing in floating model space, dont use any zoom cammand as this will upset your scale and you will need to redo your scale command.
then to set the dimension scale to this new vp in paper space you must leave the vport layer on and type
dim (return)
dimlfac (return)
then the command line tells you what the dim scale is set to so just type v and click on whichever vport you want dimension off and the dimscale will jump to the scale of the vport, hey presto.
remember if you have different vports at different scales, you will need to carry out this dimlfac exercise every time.
hope this helps.
regards, conskee