Hi Raquel,
You can use IIF expression in text values to display the data as read only check boxes. Please refer the below steps to view data as checkboxes.
1. Create a textbox and set font family to Wingdings.
2. Insert an expression (“=IIF(Fields!IsMinimum.Value="false",chr(254),"o")”) on the textbox.
We have created a report based on this and it can be downloaded from eh following location.
Please let me know if you have any questions.
Anandakumar S