There is now an equivalent tool for .NET, the P/Invoke Interop Assistant (http://www.codeplex.com/clrinterop ). Not surprisingly it does a little bit more, so as well as enabling you to look up the signature for a particular call, it will also translate snippets of C code.
Notice that it generates required structure definitions to go with your function call!
I also noticed that the P/Invoke Interop Assistant generated code that used the DllImport approach to setting up the API call. I expect this question has been answered loads of times before, but what are the advantages of using DllImport rather than Declare in your VB code? The obvious answer is that DllImport is a .NET way of doing things, but for VB6 programmers of the Declare statement looks much more natural. DllImport does offer much finer control over the way the call is made, but unless you need this fine control you can stick with Declare.