Yes-ish, probably maybe - see http://www.b4x.com/forum/questions-help-needed/1854-com-controls.html#post10125 Ideally you need VS with which it is dead easy on the desktop as it builds the Interop Assembly for you which you can also do at the command line with the tlbimp.exe utility. Then you need to write a Basic4ppc library in C# or VB.NET that uses the Interop Assembly to expose the bits you want to Basic4ppc.
OK, thanks, that doesn't look that promising then and probably not worth the trouble. I do have VS6, but I don't know about any .net. It looks that as you need .net coding in any case it might be easier then to re-write the ActiveX dll in .net.
Probably as you need to write the wrapper library in .NET anyway. The free Express versions of VS200x will do desktop libraries (I think) but you need VS2005 Standard or VS2008 Professional (ouch!) to do device libraries. SharpDevelop is free and can do devices as well but I believe it is a bit more finicky to use than VS but I don't know as I have never tried it. I use VS2005 Standard myself.
According to Microsoft the "Visual Basic 2008 Express includes a migration wizard that will help import existing Visual Basic 6.0 projects. You may need to make some manual adjustments to the code you port over, but the migration wizard is a good first step towards moving your code forward."