batch file - Set enviroment variable setx

I am setting a environment variable with setx(win7) in a cmd , that I started from a batch file, if I close the shell an open a new from batch file again and use Set command to check it, I do not get this new variable. I can see the variable via windows and regedit, had someone an Idea what I do wrong?

EG.

Batch:

Rem set some local variables

Set varableA="test"

...

Start /B cmd.exe /k

In the opened shell:

Setx -m variableB value --> set system envirtomet vartiable

Close shell an run batch again

In the new shell:

Set var

And thgerre is not variableB but in Windows an registry I can see it