To highlight cells based on dates that are 30, 60, or 90 days out, you can use conditional formatting in Microsoft Excel. Here are the steps:

1. Select the range of cells that you want to apply the conditional formatting to.
2. Click on the "Conditional Formatting" button in the "Home" tab of the ribbon.
3. Select "New Rule" from the drop-down menu.
4. In the "New Formatting Rule" dialog box, select "Use a formula to determine which cells to format".
5. In the "Format values where this formula is true" field, enter the following formula for 30 days out: =TODAY()+30=A1 (assuming your dates are in column A)
6. Click on the "Format" button and choose the formatting you want to apply to the cells that meet the criteria.
7. Click "OK" to close the "Format Cells" dialog box.
8. Repeat steps 5-7 for the 60 and 90 day formulas, changing the number in the formula to reflect the number of days out you want to highlight.

That's it! Now, any cells that meet the criteria you set will be highlighted with the formatting you chose. Note that you can also adjust the formatting for each rule by clicking on the rule in the "Conditional Formatting Rules Manager" and clicking "Edit".