Maybe:
=IF(C4="wd",MAX($C$4:$C$23),C4)+IF(D4="wd",MAX($D$4:$D$23),D4)+IF(E4="wd",MAX($E$4:$E$23),E4)+IF(F4="wd",MAX($F$4:$F$23),F4)+IF(G4="wd",MAX($G$4:$G$23),G4)+IF(H4="wd",MAX($H$4:$H$23),H4)+IF(I4="wd",MAX($I$4:$I$23),I4)+IF(J4="wd",MAX($J$4:$J$23),J4)+IF(K4="wd",MAX($K$4:$K$23),K4)+IF(L4="wd",MAX($L$4:$L$23),L4)+IF(M4="wd",MAX($M$4:$M$23),M4)+IF(N4="wd",MAX($N$4:$N$23),N4)+P4