再建好模后，在配制选项里点BUILD的时候出现以下错误，我也进行了一些操作，但不是很懂错误是什么意思，请高手帮帮忙

Error using ==> RTW.makertw.make_rtw

Error using ==> rtw\private\issue_inv_comp_env_val_error

Invalid setting for environment variable MSDevDir or DevEnvDir.

The setting is: ''

You can verify the setting by checking for the existence of:

%MSDevDir%\..\vc\bin\vcvars32.bat          (for Visual C/C++ 5.0)

%MSDevDir%\..\..\vc98\bin\vcvars32.bat     (for Visual C/C++ 6.0)

%DevEnvDir%\..\tools\vsvars32.bat          (for Visual C/C++ 7.0)

You must define MSDevDir or DevEnvDir to be:

set %MSDevDir%=\sharedide      (for Visual C/C++ 5.0)

set %MSDevDir%=\common\msdev98 (for Visual C/C++ 6.0)

set %DevEnvDir%=\common7\ide   (for Visual C/C++ 7.0)

This error may be due to an invalid preference file:

C:\Documents and Settings\lixiang\Application Data\MathWorks\MATLAB\R14

\mexopts.bat

Please run "mex -setup" at the MATLAB prompt to correct

我按照上面写的进行了一下操作

>> mex  -setup(mex 这是什么意思啊？)

Please choose your compiler for building external interface (MEX) files:

Would you like mex to locate installed compilers [y]/n? y

Select a compiler: 从这里看好像需要C/C++的软件，是吗？

[1] Lcc C version 2.4 in D:\MATLAB7\sys\lcc

[0] None

Compiler: 1

Please verify your choices:

Compiler: Lcc C 2.4

Location: D:\MATLAB7\sys\lcc

Are these correct?([y]/n): y

Try to update options file: C:\Documents and Settings\lixiang\Application

Data\MathWorks\MATLAB\R14\mexopts.bat

From template:              D:\MATLAB7\BIN\WIN32\mexopts\lccopts.bat

Done . . .

>>