Use TV as a HDMI-switch

[borgja_jcc]

Hi, 
I just bought the KDL-55W905a, and my home theatre does not have ARC.
Hence I had to connect all my equipment to my TV via HDMI, and connect and optical cable to my home theatre system.
Sound now works perfectly, with Dolby Digital and DTS where this is available
However, now i cannot control sound volume via TV remote, I have to have the remote for the HT available for that. 

Is it possible to fix this in some other way? Can the TV remote be programmed to control volume on HT instead?

My equipment: 
KDL-55W905a w/IDTV for Canal Digital
BDP-S790 Blu-Ray Disc Player
HT-SF2000 Home Theatre System
DIY HTPC, Windows8

PC and BD-player are connected to TV via HDMI, and the TV to HT via optical cable.