SQL select into define new column

SQL select into define new column

I have a statement like this:
SELECT field1, field2, MyField = NULL
INTO NewTable
FROM OldTable
This does what I want with one exception: the field I created MyField and
filled with NULL is an INT type and I'd like it to be a VARCHAR type. I
don't know how to modify the same statement to create the new field with
the VARCHAR type.
Thanks.