checkbox or interface tool to replace subject line of email, how to do it?

[wonka1234]

Hi,

I am having trouble with incorporating this logic -

Keep email subject as is - or Change the value based on checkbox

How do I update the checkbox/update value tool ? 

I have the update value connected to the email tool and subject with update value with formula selected.

How do I do this?

Thanks.

[wonka1234]

trying to use this formula - 

If [#1] = 'True'
then [Destination] = "Update"
else [Destination]
endif

meaning - if checkbox is selected update the subject to "Update" else leave it as is.