In order to be able to run the Relative Expression Software Tool correctly 
in all Microsoft Excel versions and to maintain the macro-virus protection 
for unknown documents as well active, it is recommended to activate 
the 'Trust all installed add-ins and templates' checkbox under

Tools => Macro => Security => Trusted Sources
or
Tools => Macro => Security => Security Level

and to    set the 'Security Level' to 'Medium'

as shown in the following two screen shot pictures.