If they refuse, we will appeal their decision.

Eğer reddedersen, onların itiraz edecek.

Am I correct? 

My try as a learner -

Eğer reddetirseler, onların kararını itiraz edeceğiz

But wait for a native speaker´s corrections 

 If they refuse, we will appeal their decision.

turkish=Eğer redederseler ,onların kararına itiraz edeceğiz.

henry´s:Eğer redde-tir-seler, onların kararın-ı- itiraz edeceğiz-(´kararını´ ex:onun kararını beğendim)

good jop anyway

Thank you both so much

My husband´s English is good, so I have been a little lax in learning Turkish as fast as I should be.  I can usually ramble on a few sentences to him when I am practising, but right now we are in the middle of trying to emigrate him to Canada and it´s not a good time for miscommunication.

thanks for your corrections kdr