I have to add a correction to this post. I have recently discovered it is possible to pass a double as 2 integers to a function in a dll with a double parameter. This was figured out ages ago actually for OpenGL functions.
That could come in handy. What's the syntax for doing that, markcw? Do you just add the singles together in the dll function call (eg. ExampleDllFunctionCall( singlevar1 + singlevar2 ))?