vs 2010 vb adding a date function to a dataset column expression

Trying to add a date function to a dataset table column expression but 'Property Value not Valid' error results.

I want to have a calculated column in a dataset that gets the current date then use this current date for comparison to other columns, for example, to check if a item has expired.

Have tried the 'get date()' function as well as 'dateadd()' function but can't get it to work. Adding the column using the dataset designer.

Any insight would be appreciated....