Hello, Esteban,   

The ExpressionFormattingObject expects a fixed value for the expression like below:

        Dim obj1 As New ExpressionFormattingObject("MyCondition1", "CreatedOn > #09/30/2019#", True)
        obj1.CellBackColor = Color.YellowGreen
        Me.RadGridView1.Columns("CreatedOn").ConditionalFormattingObjectList.Add(obj1)

You can construct  the expression at run time considering the value of DateTime.Today.

An alternative solution that I can suggest is to handle the CellFromatting event where you have direct access to the CellElement.Value property and can add an if statement checking the date value of the respective cell. Please refer to the following help article which demonstrates how you use the event and apply the desired style to the respective cells: https://docs.telerik.com/devtools/winforms/controls/gridview/cells/formatting-cells

I hope this information helps. If you need any further assistance please don't hesitate to contact me. 

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik