Is it possible I can entry purchase & sale in one invoice?

We do a travel agency and we keep excel sheet for sales & purchase figure. from their we again enter into Instead of double job, can we get similar format. Giving below some example.

Purchase order number : (Manuel entry)
Sales Order : (Automatic entry)
Customer number: (manuel entry)
then following information same as per your current system
qtry. Purchase then Sales Price
then automatic purchase figure will show in Purchase & sales figure in Sales

But where does the purchase figure come from to be automatic?
Don’t Travel Agents like Insurance Brokers only receive a commission and that commission is their sales - income.

Isn’t the airfare (say 660.00) the sales figure for the airline, not the travel agent.
If the travel agent receives a commission of 5% then the travel agent sales figure is 33.00 and the balance of 627.00 is held in a BS - Liability - Trust A/c for payment to the airline.

Not automatic, need to enter both figure manual but instead entry into two separate invoice, can we select one invoice put purchase fare and sale price. First select supplier, then select customer the purchase price then selling price that’s it. When we select supplier, the purchase figure will show, when we select customer then the selling price will show.