Google Sheets Conditional Formatting – Custom Formula Issues

First of all, sharing your sheet or at least a copy/example is going to get you a much better answer more quickly.

I attempted to recreate your spreadsheet as best I could given your description (completely guessing on the calendar sheet).

Based on my example, all the cells in Calendar!B6:X37 contain a unique date. Each cell takes its date, and searches for it in 'Training Classes'!E:E. If it finds a match, then that cell gets highlighted yellow.

The formula I use for the conditional formatting is:

=ARRAYFORMULA(COUNTIF(INDIRECT("Training Classes!E:E"),B6:X37))

The formula you were using:

COUNTIF(indirect("Training Classes!$E:$E"),A1)>1

I believe this wasn't working because: You said the calendar was in B6:X37, yet you reference A1 (your working formula example uses S27). Also, you are missing an = at the start of the formula, and the >1 appears to be unnecessary.

• conditional formatting of whole row with a custom formula: =IF(LEFT($A1, 3)="Sat", 1, 0)