You cancelled the parameter entry, not the opening of the form.  Access cancelled that for you, and that's why you were told that.  The error you got was actually a run-time error.  To not see that, you need to either (1) rewrite your code so that a run-time error would not occur in the first place, or (2) trap the run-time error with On Error statement.  Number (1) is the more desirable option, because you want to avoid run-time errors as much as possible.  To rewrite your code, consider not using parameter queries.  Find another way to get the user's input, one that does not cause a run-time error when the user cancels the entry.  Then you feed the user entry into the query (as a criteria, perhaps).