Changing the Portamento time in a Combi

[Mersip]

Hi everyone,
I have a Programme for a polymoog-type sound, and it has portamento (assigned to SW1). I've set one of the assignable knobs (Knob1) to Porta Time (CC#05), which enables me to change how fast or slow the portamento goes.

My problem is that I have created a Combi using this Programme (in fact, it is currently the only Programme in the Combi). I've copied the IFX and MFX for the Polymoog and set up the same Portamento functions (SW1 and Knob1). While the portamento switches on and off, the Porta Time function doesn't work. I've checked to make sure the function is activated (Menu, Midi3). Any thoughts???

I'm trying to play a YES song ... Perpetual Change.

Thanks

Peter