You cannot call arbitrary functions in a DLL directly from Java.
You'll need to write a Java class, to define the interface of your DLL. Some of the methods of this class would be declared native. The native methods would be implemented in C or C++ and would be compiled into another DLL. Your Java code need to load this DLL, maybe with System.loadLibrary().
The native implementation of these methods would translate the data between the Java types and whatever types your FoxPro DLL uses. The native implementation would also be responsible for loading the FoxPro DLL.
Betty Rubble? Well, I would go with Betty... but I'd be thinking of Wilma.