This is the Excel sheet without additional constraints. How do I incorporate the constraint for this question on Excel? My Excel formula for the cell G$3$ is $=$SUMIF$($$A$$3$:$A$$16,$F$3,$$D$$3$:$D$$16)-$SUMIF$($$B$$3$:$B$$16,$F$3,$$D$$3$:$D$$16)$ and I tried $=$G$4+$G$6>=1$ for the problem but it failed to find a route that connects $($Solver chose $2->5->8,$ without considering $1->2$ even though I made sure to add the constraint for node $1=1)$