Focus problem with embedded OCX

Hi, I have written OCX in C++ displaying DWG model graphics. I embedded it as a control to the VB form. On the form there are also several buttons controlling the state of the OCX. Everything works great, but the only issue is that when I click one of the buttons (e.g. orbit view, pan) and then try to manipulate the drawing, OCX doesn't get MOSEMOVE events while i'm holding mouse button for the first time. This is until i release mouse button and then everything is back to normal and OCX gets every MOUSEMOVE event while holding MB. This seems to be problem with focus but calling Select() and Focus() functions on OCX control in Button.Click event handler doesn't solve the problem. I'm sure it's not OCX problem because in other applications (not VB) this is not an issue.

Thanks in advance for any advice.