At the start of your mk.bat file, the command is probably like this:

   csc.exe /t:library /out:AssemblyName.dll ........
or 
   vbc.exe /t:library /out:AssemblyName.dll ........

What you'll need to do is update the csc.exe or vbc.exe part with a full path, like this:

   C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322\csc.exe /t:library /out:AssemblyName.dll ........
or 
   C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322\vbc.exe /t:library /out:AssemblyName.dll ........

That may be enough to get you going. If not, please show me the content of your mk.bat file.