Supported Functions in expressions in XML Business Rules

Hello experts,

I was trying to update a datetime field via an expression in a Business Rule xml message using the below:

<update_task>
<task>
    <task_id>@task_id</task_id>
    <user_def_dttm3>@expression[Now()]</user_def_dttm3>
<update/>
</task>
</update_task>

What I was wondering is: How can i use the Days(Integer) function in conjunction with the above to update a datetime property with the current datetime plus 1 day (same time but tomorrow)?

Best Regards,

G.T.