[NTG-context] Lua & MP

Hello, is it possible that Lua gets value of a MetaPost variable? Let's have MetaPost code: z11=(0,0) z12=(1,1) z21=(0,1) z22=(1,0) aa[z11,z12]=bb[21,z22] So now aa = bb = 0.5. And I'd need to access MetaPost values 'aa' and 'bb' from Lua (e.g. in Lua: "local a = mpost.aa, b = mpost.bb"). Is it possible somehow? Regards, Lukas