I would suggest reviewing the TestComplete doc for the ReadyAPI Test Editor - specifically Overrides and Properties: https://support.smartbear.com/testcomplete/docs/working-with/integration/ready-api/editor/index.html
You can set a Project.Variable as a project property to use in your API test. And although the docs don't explicitly explain how to pass the variable at runtime - I believe they cover it in the SmartBear Academy video somewhere.
You can try creating and setting a new Project.Variables.hostName > setting this as a project property in the API test editor > and using the following as the Host in your Overrides: ${#Project#hostName}
^^^ here's a post about it that may be helpful [here]