Outlook Filter By Subject with a variable

I have a question related to filter as i try putting filter as a subject where it contain
a day where i assign using a variable but i got some error,
cant be phrase

my subject contains
MLO for 15/06/2021 Day shift

where i try to filter by
“[Subject]='MLO for '” + dates + “Day shift”

dates is today.AddDays(-10).ToString(“dd/MM/yyyy”)

but it dont work how can i do this to mark this subject contains as read?