Some years ago Que Hales of Pool Chlor and the JSPSI (Journal), published a method of doing just that, using alkalinity tests.

You could do the same thing, using a K-1766 and salt additions. Your accuracy would be limited by the accuracy of the tests AND the salt addition. In other words, you'd better weigh the salt. You'd need to test salt levels before and after the addition. I doubt that you'd be more accurate than direct calculation, when pool layout is simple (rectangle, etc.). But, with free form pools in irregular shapes, you very well might get superior results.