Importing a function from a DLL compiled using another language

[jm]

This is purely a research exercise on my part with limited knowledge.  I'd be grateful if someone could tell me if there's a way in which I can import a function from a Windows DLL that I created using a non-C language compiler on Windows.

The other language compiler has understandably given me only a .DLL and a .LIB but the examples I've seen, where a DLL is used within C, appear to show a .H header is needed.  What should I create in the .H file, or is there another way?

The DLL I created is called JDL.DLL and it contains a function called myfunction() to accept a float value and return the result also as a float.  Can anyone help with this please, thanks.