(vlax-curve-getPointAtParam ename parameter)
The vlax-curve-getPointAtParam function finds a point of a specified entity which has a specified value of the parameter.
ename specifies an entity to be evaluated.
parameter specifies the parameter value of the point on the specified entity as floating-point number.
The function returns a list of three floating-point numbers representing the calculated point in WCS coordinates. If the function fails, it returns nil.
Examples
: (setq startpar (vlax-curve-getStartParam en))
: (setq endpar (vlax-curve-getEndParam en))
: (vlax-curve-getPointAtParam en ( / (- endpar startpar) 2))