MIXING SPOT COLORS/PANTONE COLORS

I am in the t-shirt business and we are always mixing percentages of pantone colos. example(60% pantone 185 with 40% pantone 123 to get a shade of orange.)

I am curious if there is a way to do this within a color pallete or wherever in order to print separations correctly.  I have always had to go back and trick the file and mix process

colors to print the seps from within corel.  There has to be a better way.

thanks