Determining Exact Receive Frequency in mHz

For years I have used my Flex-1500 to measure received carrier frequencies to the nearest millihertz. This required correcting for the F-1500 DDS's offset at each VFO frequency. I understand that this is significantly more complicated with the 6000 series, but possibly the exact Rx and Tx frequencies could be calculated internally by the firmware. If that were to be done, could the exact 'VFO' frequencies then be read with a new, or modified CAT command? This would satisfy us FMT nuts and not require any SmartSDR enhancements. John Stuart, KM6QX