Sum in form

[Shaamel]

How can I get Total of a text filed in a form. Default
view of this form is "Continuous Forms". I used this
formula but didn't work....
=SUM(Text11)
I added two new text fields. Text 11 and Text 12 in a form.
Text 11, where I am entering numbers. Note: This is a
Continuous Form. so I can add numbers in multiple times in
mulitple rows, And Text 12, where I am using this formula
in control source of Text 12.
=SUM(Text11).
When i change the view from design view to form view , it
shows me "#Error" in text 12.
Please, help me to resolve this issue.

Thanks
Shaamel