Veteran defender Uhlenbeek has joined The Terriers on trial after being released by West Yorkshire rivals Bradford City.
Young midfielder Fowler joins up from Coventry City with Jackson eyeing up a loan swoop for the Welshman.
Jackson is hoping Uhlenbeek will solve his search for a right back and will also put Fowler through his paces during a pre-season friendly.
"Let's face it, we need a right back and Gus fits the bill," Jackson told the club's official website.
"He's got the experience needed to play at this level and has played at a high level for most of his career.
"I have shown him round the facilities and he was impressed with the set-up.
"Lee's also training with us and he's a real quality player. He's going to be here for the next week and will feature in our first pre-season friendly against Wakefield and Emley next Tuesday."
Meanwhile, Jackson has confirmed that he is talking to Oldham Athletic utility player Tony Carss about a move to the Division Three squad.
Carss rejected an offer to join Second Division side Colchester United because of his desire to stay in the North West and may consider a switch to The McAlpine Stadium as an ideal move, with The Latics currently suffering a major cash crisis at Boundary Park.
