How to Average Sales Data based on a matching date

Good morning all! Hello from Ontario Canada!

I've got a multi data sheet here and I'm trying to get the worksheet to calculate a gross average based on a date selected from a drop down menu and data from another sheet.

As you can see, 'Deal Tracking' carries plenty of data entries, all starting with a date. I'd like drop down in B2 of 'B-SHEET' to select a date and for the worksheet to pull all the sales number from the 'R' column of Deal Tracking and automatically average out based on the amount of results returned for that date and display it in 'B-SHEET' B7.

I'm scraping my head over this one even though I'm sure I'm close to solving it, I've decided to search for some help!

All help is appreciated!

Allen.