Lady Marmalade, meet Mrs. Chicken of the Sea. Patti LaBelle and Jessica Simpson will headline the seventh annual ''VH1 Divas'' concert, the music channel announced Monday. Both the R&B legend and the MTV ''Newlyweds'' star are newcomers to the ''Divas'' concerts, which have raised millions for music education in public schools through the VH1 Save the Music Foundation. As in previous years, the show will be held at the MGM Grand Garden Arena in Las Vegas. The concert will air live on VH1 on April 18, with other performers to be announced in the coming weeks. LaBelle and Simpson may even perform a duet, depending on how long it takes LaBelle to explain to Simpson what ''Voulez-vous coucher avec moi ce soir?'' means.