Dimension with opening height according to door sill.

[dchatrath]

Hi. 

I have modeled a door with a sill height of 0.6 m. The actual dimensions of the door should be 2.9 m x 1.7 m. The actual opening dimensions should be 2.9 m x 2.3 m. When I dimension the door, the dimension line indicates the height of the door and not the opening. How can I get it to indicate the opening height?