My greyhound misses my ex dreadfully.How can I help him?

I split up with her last week and he has been whining for her since. She used to take him during the day while I am at work so now he only sees me at my 2 breaks, lunchtime and then at 5pm when I go home. He cries for her and her kids all the time and I feel terrible as it was me that made the split. A reconcilliation with her is out of the question and I do not wish to speak to her until the dust has settled. There is no-one else that can take him during the day. How can I cheer him up?