first off there are ds18s20 and ds18b20 devices each would need slightly different treatment.
then you need to decide the resolution and "sign" you wish to display.
if negative[below zero] temps are involved the the sign bit of the result must be properly accommodated before results are scaled.
once you have a unsigned scaled binary result pbp can extract the digits with the DIG function.
the digits can then be displayed along with the sign and decimal point if needed as you desired.