Emulating 74125 Buffers

Environment: Quartus WE 9.1 SP2, MAX7000S, EPM7064SLC44.

Trying to obtain tri-state output pins using GED and instances of TRI buffer. I can successfully create, compile and simulate two outputs, but for three outputs up comes the message:

Error: Can't route source node "OE" of type max_io to the OE port of destination node "OUT" of type max_io.

I understand the Tri-state mechanism is within the I/O block and not within the macrocells. But the MAX7000S datasheet shows for each I/O block the tri-state control is muxed with sources coming from Vcc or Gnd or from six other sources, including macrocells.

Is my understanding correct? If so, how does one nominate the source for the tri-state's OE?

Regards,

Workalot