TextBox to display value in existing cell then update it

Hello!

I've been trying to figure this out for a couple of days- no luck. I built a UserForm that populates an Excel sheet based on some simple choices and data entry.

First, the user must choose 2 values from 2 dropdown menus:
1. Month
2. Facility

Then they are to enter 2 numbers into 2 text boxes: TextBox1 and TextBox2. These numbers are recorded on the spreadsheet in columns D and E, respectively. The target row depends on the Month and Facility selected.

Now here's the problem: When the user initializes the UserForm, then picks Month and Facility, I'd like TextBox1 to display the current value in the corresponding D cell. The user can then choose to keep the shown value or update it then hit Enter to populate the spreadsheet.

I'm loosing my mind over this! I feel like it's probably a very simple one-line code, but for some reason I just can't get it right!

Thank you!