They just control the appearance of the dialog box when it first opens. From experimentation: -
text- appears in 'Find What' box
in_num 1 - Formulas, 2 - Values, 3 - Comments
at_num 1- Find entire cells only box is checked, 2- unchecked
by_num 1- By Rows, 2- By Columns
dir_num Not sure, presumably controls the Find direction, but I don't think there's an option on the dialog for it
match_case True Or False
match_byte True Or False
So, you could use something like this to set up the dialog box for the user: -
Application.Dialogs(xlDialogFormulaFind).Show "TextFind", 3, 2, 2, 0, False, False