Only approximately, of course. The timer control is not that accurate. For better precision you may need to use the system "tick count" or something. On the other hand, if by "auto clicking" you mean issuing mouse clicks, I doubt you'll get it to happen as fast as 1000 per second.
Out of the 3 computers I've tested the Timer on (different combinations of Windows XP, Vista, Intel and AMD processors), they are always accurate to exactly 15 mS.
As for actually issuing the mouse clicks, I'm sorry - I can't help. I only know how to position the mouse cursor on the screen, not simulate clicks. It would be useful for me too, to know this (and for people interested why - it's just for 'visual novel' style games which lack a SKIP feature).
I have a DLL capable of doing this, as well as simulating drag-and-drops, but it does not work in VB6. It's due to the way VB6 needs the functions implemented... or something?? As you can tell, I don't really have much knowledge with DLLs. I could ask the creator of the DLL for permission to post it here though, in case someone into DLL-modifying could find it useful? Or would it be too hard to understand becaus it's compiled?
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I just made the most time-wasting post ever. >_<