Is there a way in Excel using macros or array functions etc that would allow me to create a set of random numbers that would be unique.

The random numbers would not only have to be unique with the current set but also unique with sets from previous dates.

For instance you are creating 200 unique numbers per day. Today you wanted 200 unique numbers that was also unique with the previous 200 numbers you created yesterday.

The numbers would be in a range from 1000 to 65536. The system would also have to be easily expandable which would allow for easy number generation from day to day.