Not sure formula to use for INDEX MATCH or VLOOKUP Multiple criteria

Hi All,

I'm really struggling with a a formula to pull in a certain sales value of a product, for a certain month - determined by a different month for each product, and pulled from potentially different columns on a different tab.

I have attached a sample and hope to explain below:

On Unit Sales Data Tab

In column P I have highlighted in yellow - this is where the formula needs to lay.
I would like this to return the answer £38 - which is taken using the date in Column C on the same tab, matching that date with the appropriate column in the Sales by Month Tab and then the product in Sales by Month.
I have highlighted each of the fields in both tabs for reference.

The problem is, the dates will change, so I can't work out how to select a date from one tab, then based on that date, determine which column from the other tab I need to pull the data from. I can do it manually, but that will make this a painstaking process to update.

Is anyone able to help?
Many thanks in advance.

You're a star, thank you ever so much. Works perfectly.