You could make the HEX file for the EEPROM or flash chip using a C program on your PC. You would have difficulty using the eval version of Keil to make a table bigger than 4K.

If the PC makes the table then for an EPROM memory just download to a EPROM prorammer to make the part.
If you fit a FLASH to the board then I suggest that you download the data table from the PC via UART to the 8051 which would then have flash procramming alogorithms in it to write the external FLASH chip.

Using a look up table in Keil is simple. Just declare it as some type of array in XDATA space. See the compiler manual. If you use the AT attribute on the declaration the C compiler should not try to include the while space of the array into the code image and thus you can get by making the eval compiler work for you.

Michael Karas