In this paper, we consider a system modeling an axially moving viscoelastic string under a spatiotemporally varying tension. A mechanism consisted of a hydraulic touch-roll actuator pointed at the right boundary to suppress the transverse vibrations. We adopt the multiplier method to design a boundary control law and to prove an exponential stability result. However, this result is obtained provided that the lower bound of the tension in the string is larger than its time derivative. The effectiveness of the proposed control law is demonstrated via simulations.