How to read\write clipboard from service?

Question

C++ / C#

Is there some tricky way to use user32 functions from a service (windows, clipboard) without creating an additional application?
There is a service, there is all the data for logging into an account, I can log into an account and run regular applications there with a guy. Through this application, you can establish a connection between the service and the guy, but is it possible to get access to the guy from the service without an additional application?