Hi Shantanu,
Yes this scenario can be built with RE-FX.
What you need to do is these following steps :
Create 3 BPs with different recon account in foreground, which in turn will create 3 vendors respectively in background.The standard config is available in RECACUST which creates Vendor automatically when BP is created condition that all the mandatory details required in Vendor master are updated in your BP master.
Now in Contract master data you need to assign these 3 BPs in Partner data.Create 3 Posting Parameters with different BPs assigned respectively.
Create these three conditions and in term tab of condition, use respective Posting Parameter.
So when you post the conditions, respective Recon accounts will get hit.
Hope it helps you!
Regards,
Siddharth