You can format cells based on text content using Conditional Formatting in Excel. Here's how to highlight duplicate entries:

1. Select the data range: Choose the cells containing the text data you want to analyze for duplicates.
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 dropdown menu.
4. "Format values that..." - Use a formula: In the "New Formatting Rule" window, choose "Format values that..." and then select "Use a formula to determine which cells to format."
5. Enter the formula: In the "Format values that match this formula" box, enter the following formula: `=COUNTIF($A$1:$A$10,A1)>1` (replace `A1` with the first cell in your data range and `A$1:$A$10` with your actual data range if it's different).

Explanation of the formula:

- `COUNTIF($A$1:$A$10,A1)`: This part counts the number of times the value in cell `A1` appears within the range `A$1:$A$10` (adjust the range as needed).
- `>1`: This checks if the count is greater than 1, indicating a duplicate entry.

6. Format duplicate cells: Click the "Format" button and choose the desired formatting for duplicate entries (e.g., highlight with a specific color).
7. Click OK: Click "OK" on both the "Format Cells" and "New Formatting Rule" windows.

Now, any cells containing duplicate text entries will be formatted according to your chosen style.

Additional Tips:

- You can adapt this formula for other criteria. For example, to highlight unique entries, use `=COUNTIF($A$1:$A$10,A1)=1`.
- Conditional formatting allows for more complex formulas and comparisons. Explore other functions like `FIND`, `SEARCH`, and wildcards for more specific text matching.