What is stopping you ?
Oh well, here we go:
Set the setpoint for an IEC timer to whatever full period the sinus curve must have. Then program it to restart when it times up.
If it is set to 30 seconds for example, it will go through 0-30000 milliseconds.
//This is the part where you calculate the radians:
//(TimedTime/Fullcycletime) x 2 x Pi
L "Timer".ET
DTR
L "Timer".PT
DTR
/R
L 6.2831853 // 2 x pi
*R
T "rRadians"
// this is the part where you generate the sinus value
L "rRadians"
SIN
T "rAmplitude"
edit: I had swapped .ET and .PT.