Here is the original, that doesn't work for me in VS Express:
devenv "%w" /build "%bn" /project "%rm"
And here is a version that seems to work:
msbuild "%w" /t:Build /p:Configuration="%bn"
Thanks for the comment, it lead me to take some time and figure it out.
"%w" becomes the .sln file
"%bn" becomes the word "Debug"