How to measure voltage from ADC and display in dB?

I'm taking an output voltage from and ADC and intending to display in dB. from my radings, I need to get voltages over a period of time, square it and divided it over number of samples. VRMS =Sum of (square Voltage)/number of samples. Then i need to perform 10* log (VRMS) for power dB or 20* log (VRMS) for voltage in dB.

Any clues: I heard this can be done by software or hardware.

If software, how to incorporate software in ISE Webpack?

if hardware do i need adder, multiplier, divider for VRMS. and for log I can't find a method. for final display in dB, may need floting point?

Anyone can provide my tips or sample codes, or let me knowwhere can I find.

Thanks in advance.

jamie