The Dutchman's future has been the subject of much speculation over the summer, with Real registering their interest in capturing the Holland winger.
And despite Chelsea's insistence that Robben is going nowhere, Calderon remains hopeful a transfer will soon be completed.
He told Marca: "We are advancing and I hope the deal comes to fruition in the next few days.
Drenthe keen to make Madrid move
"But Chelsea have to decide to sell first."
Speculation that Robben was on the verge of leaving Stamford Bridge heightened when he was left out of the Chelsea squad who played LA Galaxy over the weekend, but Blues boss Jose Mourinho insisted the 23-year-old's exclusion was due to an ankle injury.
Robben faces stiff competition for a berth in Mourinho's starting XI this season following the arrival of France international Florent Malouda at Stamford Bridge.