I've created a dll in c++ that runs a 4th order Runge-Kutta on user supplied data. I want to use it in a particle simulation, which I already have in vb.net. The trouble is I have no idea how to call the dll from within vb, any ideas? ps- I've tried using the info provided on msdn, but I'm not sure if I'm doing it right. Basically the dll file is called "RungeKuttaDLL.dll", the lib file is called "RungeKuttaDLL.lib" and the function for export within the dll is called "RungeKutta". msdn gave me this info: Private Declare Function RungeKutta Lib "c:\Documents and Settings\PB Customer\My Documents\Visual Studio Projects\VB\NumericalMethods\RungeDLL\RungeKuttaDLL.dll"(ByVal X0 As Double, ByVal Y0 As Double, ByVal H As Double, ByVal N As Integer) As Double It doesn't work though.