Ever tried juggling chainsaws?
This is actually surprisingly hard, it involves a technique called subclassing, subclassing is the VB equivalent of chainsaw juggling, i could explain the basics but i might as well just give you some chainsaws and a juggling book, If you go to the VB API site in th side bar there should be some in depth articles there or if you want I could post up the code for the control (I need all the subclassing practice i can get) but subclassing is a good techniqu to learn so if you're quite familiar with the API you should have a go.
If you know about subclassing the message you want to intercept is th WM_NCHITTEST Message the lparam is a C++ word copy this into an array of 2 integers using the copy memory API then put the 1st integer into the x of a POINTAPI structure and the 2nd into the Y value, then use the screentoclient API to convert these into usercontroll coords
if these coords are over one of your handles set the return value to HTTOPLEFT, HTTOP, HTTOPRIGHT etc depending on which handle you're over, these handles will then act like resize handles for your control. Remember to unsubclass the usercontrol before the program ends, you can do this safley by intercepting the WM_destroy message.
Otherwise just post up a message and I'll do it for you.