can i get it without using another query and button showing me all the items in the table except for status "completed"
No. Why?
Your current criteria is:
Where Status = Forms!yourform!cboStatus
The criteria to get all except "complete" would be
either:
Where Status <> Forms!yourform!cboStatus --- assuming you want to be able to select any value for <>
OR
Where Status <> "Complete" --- if you want to hardcode the value
As you can see, the "not" solution uses a different relational operator. Although queries take parameters, the parameter only replaces a data value as you can see in the two examples where the Forms! reference fetches a value which in the third example is hardcoded (a literal value in quotes). The relational operator is fixed. Unless you build the SQL on the fly, there is no way to change it in a saved querydef.
PS - always be conscious that when you are using not in the relational operator, null values will not be excluded. So, in this case, if the Status is required, you won't have a problem with <> "Complete". However, if Status is not required and so some rows might be null, the rows with nulls will NOT be returned because of the way null compares work
Where Status <> Null - will always return false (ie no rows)
Where Status = Null - will also always return false (ie no rows)
To include nulls in the set of rows with Status <> "Complete", you would need to explicitly check for nulls:
Where Status <> "Complete" OR Status Is Null
