If that's what you have on hand..go for it. You might need to add a very small amount of turmeric to the mix if you're grinding seeds yourself.
Consider getting some Coleman's dried english mustard. (in the little yellow tin).
It can be used in other things: Hot Chinese mustard. Just mix it up with cold water and stir with a fork, the more you stir--the hotter it gets. Let it rest for 15 mins to use with egg rolls. Or mix that with honey for a dipping sauce for chicken strips or veggies; it's great on carrot sticks (very spicy dipping sauce).

It's close, but if you're grinding the seeds yourself you'll wind up with little pieces of the hull that won't grind. You'll have to sift those out and the ground mustard seed will be a little stronger than dried mustard.