Yes, there is an opposite function to Concatenate in Excel called "Text to Columns". This function can be used to split data that is combined in one cell into separate cells.

Here are the steps to use Text to Columns to split first and last names into separate cells:

1. Select the column that contains the combined names.
2. Click on the "Data" tab in the ribbon at the top of the screen.
3. Click on the "Text to Columns" button in the "Data Tools" section.
4. In the "Convert Text to Columns Wizard" that appears, select "Delimited" and click "Next".
5. In the next screen, select the delimiter that separates the first and last names. This could be a space, comma, or another character. Preview the results in the "Data preview" section to ensure the names are split correctly.
6. Click "Next" and choose the format for the two columns that will be created. You can choose "General" for both if you're not sure.
7. Click "Finish" to split the names into separate columns.

After completing these steps, you should have two columns with the first and last names separated. You can then delete the original column with the combined names if it's no longer needed.