MOTM

Hey MOTM'ers,

I have a 2 osc system with a few filters, e.g.'s and 1 VCA.  So far 
I haven't done much FM with my modular b/c from what I understand, I 
need a VCA for the modulating signal, and another VCA for the 
carrier.  Since I only have 1 VCA, I've been wondering if there are 
other ways around this, such as sampling some waveforms from my 
VCO's and using the envelopes in my sampler to provide the envelope 
for the modulating signal.  Can this work?  

Does anyone have any experience working this way or have any 
suggestions?

Thanks,
-Matt