I'm just a visitor around here, but you seem to be trying to fight a design
that's been in place for around two decades. Mouse Up fires every time you
release the mouse button.

I dropped a textbox on a form in VB6, added a few debug.prints and got the
following output when I double-clicked.... (fwiw, the numbers are just the
VB timer value at the time)

'Form1:Text1_MouseDown       37502.56
'Form1:Text1_MouseUp         37502.64
'Form1:Text1_Click           37502.64
'Form1:Text1_DblClick        37502.71
'Form1:Text1_MouseUp         37502.81

So, if you're processing in MouseUp, seems like setting a boolean variable
called "ProcessMouseUp" or something similar = True in MouseDown and testing
that variable in MouseUp would be easy enough. Once the code in MouseUp
runs, reset that bool to False. Since MouseDown fires only once, the next
time MouseUp fires, your test should determine whether or not to take
action.

If you are using the VB2005 TreeView control, you should look at using the NodeMouseClick and/or the
NodeMouseDoubleClick events rather than the standard Mouse Events.

Gene