you can use these two:
VST Host which acts as realtime VST processing unit. It allows you to chain any VST plugins between input and output.
VB-Cable which is literary virtual input/output device. It allows you to use output from any program as input in another.
To join these tools set the VST Host wave-output to 'Cable input' (so the processed sound will go to virtual cable) and also you need your to change your or your VOIP software sound input to 'Cable output' (because it is output from your virtual cable)