Grabban, who has a year left on his contract, has hit 21 goals this season and has been the subject of transfer rumour since January when boss Steve Evans old club Crawley were rebuffed with an approach.
Swindon Town are thought to have placed the latest firm bid for his services today.
Evans revealed two clubs have been in contact with him this week regarding signing Grabs and that talks will continue at the end of the season.
Speaking to themillers.co.uk boss Steve Evans expected even more interest in his top scorer to come.
"Lewis will probably know of it through his agent, because that's how it works these days. There's teams in League Two, and one who has just missed the play-offs in League One after him."