Here's how to highlight the first or last entries in a sorted list using conditional formatting in Excel:

Highlighting the First Entry:

1. Select the data range: Choose the cells containing your sorted data.
2. Go to Conditional Formatting: Navigate to the "Home" tab and click the dropdown arrow under "Conditional Formatting" in the Styles group.
3. New Rule: Select "New Rule" from the menu.
4. "Format values where this formula is true" : Choose this option under "Select a Rule Type."
5. Formula for First Entry: In the "Format values where this formula is true" box, enter the following formula:

`=A1=$A$2` (assuming your data starts in cell A1)

Explanation:
- `A1` refers to the current cell within your selected range.
- `$A$2` refers to the absolute cell address of the second cell in your data column (A).
- This formula checks if the value in the current cell (A1) is equal to the value in the second cell (A2). Since the list is sorted, the second cell will be the second-highest or second-lowest value depending on your sort order (ascending or descending). For the first entry, this comparison will only be true for the top cell.

6. Formatting: Click the "Format" button and choose the desired formatting (e.g., fill color, font style) to highlight the first entry.
7. OK: Click "OK" to close the formatting window.

Highlighting the Last Entry:

1. Follow steps 1-4 from the "Highlighting the First Entry" section.
2. Formula for Last Entry: In the "Format values where this formula is true" box, enter this formula:

`=A1=INDEX(A:A,COUNTA(A:A))` (assuming your data starts in cell A1)

Explanation:
- `A1` refers to the current cell within your selected range.
- `INDEX(A:A,COUNTA(A:A))` is a formula that finds the last value in your data column (A).
- `COUNTA(A:A)` counts the number of non-blank cells in column A, essentially determining the last row with data.
- `INDEX(A:A,...)` uses that count as a row number to return the value from that row in column A (i.e., the last entry).
- This formula checks if the value in the current cell (A1) is equal to the value in the last cell identified by the formula.

3. Formatting: Apply your desired formatting for highlighting the last entry.
4. OK: Click "OK" to close the formatting window.

Note:

- Adjust the cell references (A1 and A:A) based on the actual starting cell and data column in your spreadsheet.
- These formulas assume your data is sorted in ascending order. If it's sorted descending, you'll need to adjust the comparison logic within the formulas.