As I indicated in my previous reply, for many applications, utilizing a resistor to generate a VREF for a DAC or ADC is less than ideal. Many types of resistors are inherently noisy and influenced by temperature changes, therefore not an ideal voltage reference, you would be better off with a precision zener diode or one of the many voltage reference devices available. However, depending on your specific application, a trimpot may suffice or at least it would allow you to test your design. You want to minimize current flow, so a 10KΩ or larger would be preferable, the current requirements for a VREF on a DAC or ADC is typically very low, in the uA or nA range.
As I'm not familiar with the specific design requirements, I can only offer general advice.