Problem with TablaSeleccion.getContainerProperty Value

Hi i have a question i have a column in a table

Tabla.addContainerProperty(“Price”, Float.class, null);
and i add a new item

Tabla.addItem(

new Object { -1f }, TablaSeleccion.size());

i have the table in edit mode and when i want to get the value of a row in that table

Float price;
price= (Float) TablaSeleccion.getContainerProperty(i,

“Price”).getValue();

if i put a float value like 23f ,price is 23 , but if i put “asd” ( i know that price is float) it bring me -1 , so i cant check if i put a String or a float , beacause it always bring a float , 23 or -1

Thanks!