Excel VBA product tree - Recursion may be needed

I need a sample code for my study about product tree. It will show the amount of subassembly parts to be produced. Let me explain the situation: we have subassemblies, the subassemblies also have subassemblies (with level indicators) if you check the table we will see: For the part #1 -------------------------------------------------- we need P1 and P7 to assemble a product. P1 has no stock so we need to assemble P1 from subassembly P2 P2 is also low stock so we need P3 and P5 P3 low stock we need P4 (if we come to final level and still there is no engouh stock it will show negative number ) P5 low stock we need P6 (if we come to final level and still there is no engouh stock it will show negative number ) P7 have enough stock so we do not other levels to form P7 -------------------------------------------------------------------------------------------------------