I do something very similar with the HR10-250. I wanted to be able to hold down the fast forward key to skip commercials and then have it resume playing when I let go of the key. This is what I use:
This sends the fast forward command once immediately when I press the key, so if I just tap the key it works like a plain fast forward command. If I continue to hold the button it sends it a second time to speed up the fast forwarding, then waits for me to release the key and then sends the play command to resume playing. I send the play command twice at the end because the HR10-250 sometimes missed the first play command.
The system macros referenced are just a single step with the Fast Forward or Play commands in them. I do this because the remote is in RF mode so you can't mix and match the button test with the IR codes. With RF, this button must be set to "Standalone" mode for these options to be available. If you are not using RF, you can just drag the IR codes you need into the macro in place of the System Macro steps.