Gas Usage

Hi guys, I've got a question to those who might know about gas optimization and just about Ethereum gas in general.

I'm creating a tool atm and I'm wondering, I can manually set my gas limit for any transactions but can I also preset my gas Usage as well? Or at least set a minimum gas Usage threshold for my tool. This is because sometimes I might need to win gas wars and instead of increasing the max priority I would like to preset the gas Usage instead.

For example I might set a gas limit of 600,000 and then when when I make a transaction and look at the transaction hash it only uses say 220,000 out of the 600,000 for example. Thanks.