Many times a customer will have a specific Pantone color they may need to have sublimated as part of a graphic, and they will be able to give you that specific Pantone number. This often comes up if you sublimate a company logo. You could certainly pull up the Pantone color palette in CorelDraw and color your text or graphic with that. But, more than likely, your sublimated color will be wrong.
Pantones are a set of specific colors, and most people that deal with color on a regular basis will have a printed Pantone color chart with all the Pantone colors shown on it. This will allow you to find the exact color that your customer needs, and see the hard copy of the actual color, even if your customer is on the other side of the world.
The only other way to get an accurate match would be for your customer to mail you a hard copy of the printed item for you to see the color and match with. You will then take that chart, and hold it next to your sublimated color palette and find the closest color match. If it is not an exact match, you will then need to print out a series of small color swatches and change the RGB values slightly until you find an exact match. If your customer expects an exact match, you are more than able to charge a fee for that exact match.