Set up your number of points and start/stop so that measurement points/markers coincide with your desired frequencies. Hint: numbers of points ending in "1" like 201, 401, tend to make the math work more easily.
Example: I work with SATCOM IFs so I set my analyzer to 141 points, start 850MHz, stop 2250MHz and the points are exactly 10 MHz apart.
I think that the interpolation math to give continuous markers as opposed to discrete readouts may be computationally intensive.
Best regards, Don Brant
Donald S Brant Jr