As Disp and DeltaP are assigned with units thes formula you want a see simply would be wrong.
You want Disp and DeltaP in that equations be quantities without units corresponding to units bar and mL. To Mathcad they are values with dimension, Disp=0.016 L and DeltaP=2.5*10^7 Pa. To get the unitless dimensions you have to divide it by the appropriate units which is what Richard suggested.
EDIT:
See here a "solution" - but it really hurts! You will lose Mathcads ability to calculate with units and check units for consistency that way and so its rather error prone. Its for display only and in my opinion its showing wrong, too, because Disp*DeltaP/(20*pi) IS 63.66 Nm and not 636.6 Nm. I would not recommend it.
