Comparing two columns in ssrs 2008

Hello,

I have created a report where column X is derived by an calculated expression and column Y is also has the same property. Now, I would like to add a new column, where my condition is 

if column X = "Yes" and column Y = "Yes" then my new column Z should have "Yes" in it

if column X = "Yes" and column Y = "No" then my new column Z should have "No" in it

if column X = "No" and column Y = "Yes" then my new column Z should have "No" in it

if column X = "No" and column Y = "No" then my new column Z should have "No" in it

Please help me with this.

Thanks in advance!