Calculated Value based on conditions and adding days to date

Hi,

I am very new to Nintex and trying to create a calculated value on my form to display a date based on a condition that is listed in the column personnel type then take the implementation date and add days depending on the result of the column, but cannot get it to work.  The column is blank by default until user selects an option from the drop down.

Here is what I have so far, but when I try to view the form it comes up blank and won't display.  If I delete the calculated value field from the form then I am able to display the form so I know it is related to this calulated value not set up properly.

=PersonnelType=='Key',formatDate(dateAddDays(DateTimetoImplementChanges,120, 'MM/dd/yyyy'), formatDate(dateAddDays(DateTimetoImplementChanges,365, 'MM/dd/yyyy')

Thank you!