Hi,
A BCD switch has 4 outputs. With the significance of 1, 2, 4, 8
One could connect
MSB to a 10k resistor
Bit 2 to a 20k resistor
Bit 1 to a 40k resistor
LSB to a 80k resistor and use an Opamp circuit to generate an analog voltage.
Do this for all four BCD nibbles.
Then use another OPAMP to add the 4 analog voltages but with significance of 1, 10, 100, 1000
You need very precise resistors, good OPAMPs and I recommend to use a voltage reference, because the supply voltage isn't stable enough to get good results.
*****
I wonder why you asked about 10mV of 10V, because this is only three decades, but before you speak about four decades.
Klaus