I have a price chart with the following information:

Qty: 500 1000 2500 3500 5000
Lot Price: 269 308 421 503 585
Add'l qty: .14 .14 .09 .07 .055

I am looking for a formula that will give me the correct price depending on
the quantity I type into the cell. However, my constraint is if a quantity
is equal to 501, I need to multiply it by the Add'l qty cost of .14. At the
same time if a qty goes above 786, using the Add'l qty cost will give me a
price greater than the 1000 qty lot price. Instead I would like it to use the
1000 qty lot price since it is less. The same applies for when a qty is at
1801, 3414, and 4677.

Does anyone have a suggestion that might solve my issue? Thanks