If you want to use Conditional Formatting via code (expression based formatting) you will see that it throws an exception if you set TRIM() condition.
ExpressionFormattingObject expressionCondition = new ExpressionFormattingObject(
expressionCondition.Expression = "TRIM(ContactName) = 'Maria Anders'";
expressionCondition.CellBackColor = Color.Aqua;
There is no exception if you use the same condition via "Conditional Formatting Rules Manager" form.