Units in Textfields keeps changing back

Hi, I have a simple problem which I can't get solved.

In general we are drawing in mm, so main units setting is mm. Some text fields (the "f(x)-tool" in the texteditor) should display the figures in meter. For instance:

An architectural plan with measurements in mm, showing some heights or area in meter. So in the textfield property box, units areset from "sctive units" to "meter".

After changing the depending geometry, the figure will be updated. The problem is: It then jumps back to "mm". All most all of the plans have now entirely "mm" (active unit) shown in field where it was "meter" before.

Can some one help? Is there any configuration variable for textfields?

thanks in advance, nico