I'm going through a very nasty divorce of 7 years. We are still married and yet he has a girlfriend who is giving him advice on when & where to see our kids. Hes says spenig more than a 7-3 Saturday and Sunday with them will put a bad rift between him and his girlfriend. But all I want him to do is not put a time limit on the kids. I mean I mentioned activitied that were after 3 pm and he was just like oh! Come on. Can't I set the times and places in the visitation or custody paperwork? I really don't know what to do its frustrating. And its hurting my kids.

If you can get him to admit in writing that he is putting his girlfriend ahead of his kids, you have leverage.

You will have to laugh at statements like that. He is a father. He needs to act like it until the kids are grown. He needs to look at his g/f and tell her, "You are second to my kids, but you are first in romance department. That will have to be good enough for you."

He may NEED a judge to remind him of this. He is your husband still, so what you say goes. His girlfriend has his ear, but you have his name, legally. Use the law to your advantage and don't back down on this.

There's a great scene in the new movie Apaloosa... the sheriff's is mad at the deputy so she attempts to get back at him:

HER: "He put his hands on me and tried to have his way with me."
SHERIFF (to deputy): "Is that true?"
DEPUTY: "No, I did not do that. She kissed me, but I did not do that."
SHERIFF: "Ok."
HER: "You are going to believe him over me!?"
SHERIFF: "That is correct."

And the Sheriff and the girl end up together. There is a time to put things in their right order, you need to make this man keep his priorities in order. Kids first. Period.

If the divorce and child custody agreement are not yet finalized, you may be able to specify the times he is able to come and visit the children based on their schedule. Or you can try to get him to agree to certain times so that the kids expect him during those days/times. The girlfriend can do what she wants when she wants. She obviously has him by the "you know what" and what she says goes.
However you cannot make him come, nor can you make him stay. Its clear he's choosing his girlfriend over his children, and it sucks but you can't stop that. All you can do is help and support your children.
This seems common, parents say they'll show, then they don't and yes, it is difficult for the kids. All you can do as their mom is try to explain things the best you can, NOT talk badly about him in front of them (no matter how much he deserves it!) as that will only confuse them more, and try to keep them around positive influences and activities.
Best of luck,