Hardware Compressor SideChain

Hello guys.
I have an SA4000 Hardware compressor as my 2-Bus compressor.
It"s integrated on my Mix bus in Cubase 8 as an external plugin.
What I would do is to send my mix with an High pass filter to the sidechain of the compressor in order to let him not react to the low end.
What I found that I need to do is to send all my Stems (Drums, bass, guitar…) to a mono group called Sidechain and the output of this group goes into my compressor. That works, but I would love to send my MixBus to the group Sidechain instead of all my ‘Stems’.
The problem is that all the sends are Post Insert and so the signal sent to sidechain is already treated by my comp and I don’t want that.
Is there a way to send a group/track to somewhere else but pre-insert ?