how to force to install MSI with specified language

You can launch the MSI with a specific transform by setting TRANSFORM property to the actual transform file path. Here are some articles which may help you:

• http://technet.microsoft.com/en-us/library/bb490766.aspx
• http://msdn.microsoft.com/en-us/library/windows/desktop/aa372085(v=vs.85).aspx

But if the MSI automatically selects the language, most likely the transforms are applied automatically. In this case you can try setting ProductLanguage property to set the language you want.