The ability to deploy MATLAB code to be used by Visual Basic is available with MATLAB Builder NE. With Builder NE a COM DLL can be created which can be easily interfaced with Visual Basic. The following web site has more information:
The following example project shows another way to interface with a standard DLL. It involves a Visual C++ wrapper to do the data conversion. The example demonstrates how to use two matrix input arguments and two output matrices. The example includes the necessary MATLAB files, a Visual C++ 6 wrapper that needs to be used in order to do the data type conversion between MATLAB and Visual Basic, and a VB example that demonstrates how to call the function in the wrapper DLL.