In B5 copied down:

=IFERROR(B12,0)+SUMIFS(Transfers!$D$4:$D$6,Transfers!$C$4:$C$6,'All Accs'!A5,Transfers!$F$4:$F$6,"R")-SUMIFS(Transfers!$D$4:$D$6,Transfers!$A$4:$A$6,'All Accs'!A5,Transfers!$F$4:$F$6,"R")