In T-SQL, this is allowed:

DECLARE @SelectedValue int
SELECT @SelectedValue = MyIntField FROM MyTable WHERE MyPrimaryKeyField = 1

So, it's possible to get the value of a SELECT and stuff it in a variable (provided it's scalar, obviously).

If I put the same select logic in a stored procedure:

CREATE PROCEDURE GetMyInt
AS
SELECT MyIntField FROM MyTable WHERE MyPrimaryKeyField = 1

Can I get the output of this stored procedure and stuff it in a variable?

Something like:

DECLARE @SelectedValue int
SELECT @SelectedValue = EXEC GetMyInt

(I know the syntax above is not allowed because I tried it!)