I don't have VFP9 around with its extended BINDEVENT(). Otherwise I would try to disable the clipboard using the SetClipboardViewer API call.

Step 1.
Pass the HWnd of a FoxPro form to the SetClipboardViewer. If successful, this form will receive notifications (WM_DRAWCLIPBOARD and WM_CHANGECBCHAIN messages) every time the content of the clipboard is changed.

Step 2.
Use BINDEVENT() to link WM_DRAWCLIPBOARD event to a method on your form. Inside this method, I think, the clipboard can be cleaned.

Again, I did not try this; that's just a guess.

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Added some hours later: I tried to program this approach in C# and it worked. This way the Clipboard can be virtually disabled for all Windows applications.