What should I say to him?

My husband called last night and left a message on the answering machine.  He called to wish me a happy birthday but most of the message was taken up by nearly incoherent mumbling about how he's unhappy.  I'm sorry my husband is unhappy and I'd like to tell him that but I want to avoid saying anything that would imply that I or anyone else will be rescuing him.  Helplessness is a long-running tune in my husband's playlist.  My past attempts to be provide help have been brushed or shoved off, as perhaps they should have been.  So, does anyone have any suggestions for what I can say that will convey my sympathy but also convey that if my husband wants things to change, he's the only one who can be the force for change for himself?