Hi,
Non-zero value of Err.Number indicates VBScript runtime error. Since there is no VBScript engine runtime error, this is the reason of why Err.Number equals zero all the time.
Instead, there is a test logical error when some requested item is not found. To handle this situation you can use the OnLogError event handler (see the relevant TestComplete help topic for more details).
Also, you can check if the needed item exists before trying to click it. Exact way of how to check item's existance depends on what type of combo-box the test works with.
