Fem:40yrs:taking vit d 60k iu per week for 8 weeks, then once in 15 days for a month. I get 500mg calcium from diet? Can I take 400iu with calcium?

Probably, yes. Best to speak to your treating md. As long as he/she is checking your vitamin d levels to monitor your response to treatment the extra 400 iu should be fine. Make sure you are getting levels rechecked as directed and tell your md about it at your next visit so he/she is aware. Good luck!
Need clarification. If you have been diagnosed with vitamin d deficiency then this would be safe. However, megadoses of vitamin d without frequent lab monitoring in otherwise healthy people can be harmful. 900 mg of calcium daily is safe.