How to send a key to a background window

[huzjakd]

Is this possible?
Note that the window needs to stay in the background. I don't want to set the focus for a split second and then unfocus.

[VollRahm]

I would do that with PostMessage then. I don't think it works with interception, since it only simulates Keyboard input in Kernel Space

[keytrap-x86]

See this example