Why use Coinbase to begin with? There are plenty of alternatives. Coinbase has demonstrated to be a mess because they have frozen accounts due "suspicious activity". Pretty much all credit card transactions are potentially "suspicious activity" for them. I have never done anything wrong and my bitcoins have all been obtained in legal ways and I find it offensive that I get treated as a criminal by default.
Go into a proper exchange with an orderbook.
Billy, this sounds a bit inflammatory without details.
(1) You'd help us all, especially the OP, if you share specific details of your activity so we know what Coinbase could consider "suspicious". I've used Coinbase for years and have never had an issue.
(2) What are the plenty of alternatives the OP should pursue instead? Without naming a few you don't get the OP any further down the road toward purchasing at pre-set buy prices.
To the OP, have you read this FAQ from Coinbase on placing limit orders?
https://support.gdax.com/customer/portal/articles/2426596A search on "Bitcoin exchanges that allow limit orders" returned Coinbase and Poloniex. Give Poloniex a shot if talk about Coinbase (which, to be fair, currently is experiencing a "minor outage") leaves you nervous.