Formula to copy cells from one sheet to other sheet using INDEX and ROW functions (Skipping the rows/Cells,which already have Data)

[ahasiddah]

Dear all,
Good day!
I want to copy and paste data automatically, using INDEX and ROW functions. Source sheet contains data of purchase orders and destination sheet is mix of Purchase and Sale orders.

Source Sheet[TABLE="width: 200"]
<tbody>[TR]
[TD][/TD]
[TD]A
[/TD]
[TD]B
[/TD]
[/TR]
[TR]
[TD]1
[/TD]
[TD]P.Order #[/TD]
[TD]Date[/TD]
[/TR]
[TR]
[TD]2[/TD]
[TD]P1[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]3[/TD]
[TD]P1[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]4[/TD]
[TD]P2[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]5[/TD]
[TD]P3[/TD]
[TD][/TD]
[/TR]
</tbody>[/TABLE]
Destination sheet
[TABLE="width: 200"]
<tbody>[TR]
[TD][/TD]
[TD]A
[/TD]
[TD]B
[/TD]
[TD]C
[/TD]
[/TR]
[TR]
[TD]1
[/TD]
[TD]Order #
[/TD]
[TD]Date[/TD]
[TD]Amount[/TD]
[/TR]
[TR]
[TD]2[/TD]
[TD]P1[/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]3[/TD]
[TD]P1[/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]4[/TD]
[TD]P2[/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]5[/TD]
[TD]S1[/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]6[/TD]
[TD]S2[/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]7[/TD]
[TD]P3[/TD]
[TD][/TD]
[TD][/TD]
[/TR]
</tbody>[/TABLE]

Using Formula "INDEX([Source sheet,P.Order #],ROW(A2)-ROW($A$1)", Values from source sheet are copied in destination sheet. When I write S1 and S2 manually in Row 5 and 6 of destination sheet, Contents of Row 5 of source sheet "P3" is not copied. I want to skip the copying in manually written cells (S1 and S2) and copy P3 in Row A7.
What will be the formula for it?

Thank you.