The 30-year-old is set to reach the landmark in Sunday's Six Nations clash against Grand Slam-chasing Ireland in Edinburgh.
"In this day and age, with the amount of rugby these boys play, to have the motivation and energy he has to represent Scotland, he's a special player and a special human being," Tandy told reporters.
"The pride he has for representing Scotland is brilliant to see. It'll be a huge achievement for him and well deserved."
Victory for Scotland at Murrayfield would seal a Triple Crown and keep Gregor Townsend's men in title contention ahead of the tournament's March 18 finale, when they host Italy.
"They (Ireland) are the number one team in the world for a reason but we need to look at what we can bring to the game," said Tandy.
"I think we've played really well in the first three games. We've shown lots of really positive attributes to our game.
"The boys are in a confident space and we're excited to be at Murrayfield in front of a full house playing for a Triple Crown."
Townsend is due to name his side on Friday, with Grant Gilchrist suspended for the closing two matches after the lock was sent off in the 32-21 loss away to reigning champions France that ended Scotland's hopes of a Grand Slam.
