A method of dynamical adjustment for manufacturing a thermally treated steel sheet having a chemical steel composition and a microstructure m target comprising from 0 to 100% of at least one phase chosen among: ferrite, martensite, bainite, pearlite, cementite and austenite, in a heat treatment line comprising a heating section, a soaking section and a cooling section including a cooling system, wherein a predefined thermal treatment TT, comprising at least a heating, a soaking and a cooling steps, is performed, such method comprising: A. a control step wherein at least one detector detects any deviation happening during TT, B. a calculation step performed when a deviation is detected during TT such that a new thermal path TP target is determined to reach m target taking the deviation into account, such calculation step comprising: 1) a calculation sub step wherein through variation of the cooling power, new cooling paths CP x are calculated based on TT, the initial microstructure mi of the steel sheet to reach m target, the heating path, the soaking path comprising T soaking and T cooling, the cooling step of TT being recalculated using said CP x in order to obtain new thermal paths TP x, having the cooling step replaced by one CP x in order to obtain a thermal path TP x, each TP x corresponding to a microstructure m x, 2) a selection step wherein one TP target to reach m target is selected, TP target being chosen among the calculated thermal paths TP x and being selected such that m x is the closest to m target and C. a new thermal treatment step wherein TP target is performed online on the steel sheet. A. a control step wherein at least one detector detects any deviation happening during TT, B. a calculation step performed when a deviation is detected during TT such that a new thermal path TP target is determined to reach m target taking the deviation into account, such calculation step comprising: 1) a calculation sub step wherein through variation of the cooling power, new cooling paths CP x are calculated based on TT, the initial microstructure mi of the steel sheet to reach m target, the heating path, the soaking path comprising T soaking and T cooling, the cooling step of TT being recalculated using said CP x in order to obtain new thermal paths TP x, having the cooling step replaced by one CP x in order to obtain a thermal path TP x, each TP x corresponding to a microstructure m x, 2) a selection step wherein one TP target to reach m target is selected, TP target being chosen among the calculated thermal paths TP x and being selected such that m x is the closest to m target and 1) a calculation sub step wherein through variation of the cooling power, new cooling paths CP x are calculated based on TT, the initial microstructure mi of the steel sheet to reach m target, the heating path, the soaking path comprising T soaking and T cooling, the cooling step of TT being recalculated using said CP x in order to obtain new thermal paths TP x, having the cooling step replaced by one CP x in order to obtain a thermal path TP x, each TP x corresponding to a microstructure m x, 2) a selection step wherein one TP target to reach m target is selected, TP target being chosen among the calculated thermal paths TP x and being selected such that m x is the closest to m target and C. a new thermal treatment step wherein TP target is performed online on the steel sheet.