A method and measuring tool are presented for automatic control of photoresist-based processing of a workpiece progressing through a processing tool arrangement. Spectrophotometric measurements are applied to the workpiece prior to being processed, spectral characteristics of the workpiece are measured, thereby obtaining measured data indicative of at least one parameter of the workpiece that defines an optimal value of at least processing time parameter of the processing tool to be used in the processing of said workpiece to obtain certain process results. This data is analyzed to determine data indicative of the optimal value of said at least processing time parameter, and thereby enable calculation of a correction value to be applied to said processing time parameter prior to applying the processing tool to the workpiece.