comparing frequency of two clocks

Hi Everyone,

Does anyone have any idea of how to compare two reference clocks using
completely digital logic .The problem is something like this

There are two slow ref clocks (Khz) CLKA (rc clock) CLKB (crystal
clock) and a fast sys_clk (pll clock) Mhz range

If freq CLKA > freq CLKB then
op1 = 1;
elsif freq CLKA < freq CLKB op2 = 1
else
op3 = 1;
end if;

Eagerly awaiting some solutions

arant