There are a few ways to update formulas with external references in Excel, depending on your desired outcome:

1. Manual Update:

* Option A: Edit Formula Directly:
1. Select the cell containing the formula with the external reference.
2. Look at the formula bar and locate the reference to the external workbook (e.g., [Workbook Name.xlsx]Sheet1!A1).
3. Click on the reference in the formula bar and edit the path or filename if it's incorrect.
4. Press Enter to confirm the changes.

* Option B: Update Links:
1. Go to the "Data" tab on the Excel ribbon.
2. In the "Connections" group, click "Edit Links."
3. This will display a list of all linked workbooks in your current workbook.
4. Select the link you want to update.
5. Click the "Change Source" button and locate the new source workbook.
6. Click "OK" to update the link for all formulas referencing that specific workbook.

2. Automatic Update (Security Prompt):

By default, Excel may prompt you about updating external links when you open the workbook.

* Option A: Enable Automatic Update:
1. Go to "File" > "Options." (This might be under "Excel Options" depending on your version)
2. Click on "Trust Center" in the left-hand pane.
3. Click on "Trust Center Settings."
4. Go to "External Content" and under "Security settings for workbook links," choose "Enable automatic update for all workbooks."
5. Click "OK" on all open windows.

3. Break Links (Convert to Static Values):

If you no longer need the link to update automatically, you can convert the formula to use the current value from the external workbook.

* Option A: Break Link:
1. Select the cell containing the formula with the external reference.
2. Go to the "Data" tab on the Excel ribbon.
3. In the "Connections" group, click "Edit Links."
4. Select the link you want to break.
5. Click the "Break Link" button.
Note: This will permanently convert the formula to use the current value in the linked cell, and it won't update if the value in the external workbook changes.

Choosing the Right Method:

The best method depends on your specific situation. If you need the formulas to update with changes in the external workbook, use the manual update or automatic update options. If you no longer need the link and want a static value, break the link.