Madjo, who joined on loan from Stevenage at the end of last month, marked his second start for Micky Adams' side by scoring the winner in a 2-1 victory at Dagenham on Saturday.
The 27-year-old thanked Horsfield for his help since his arrival at Vale Park.
"I've learned a lot from Geoff because he's played in the Premier League," striker Madjo told the club's official website.
"He's done a lot of finishing work with me and shown me a lot of things that I haven't done in the past, so the goal is dedicated to him.
"I've been to so many places and played for so many clubs. I've never done that amount of work with anyone else."
Port Vale last week