You can hide the formula bar easily enough. Tools/options/view, then uncheck the Show Formula Bar box.
To do it automatically for a particular file, you want the following in ThisWorkbook.
Open your file. Press Alt F11 to open the vba editor. On the left you will see a window with "VBA Project(Yourfilename.xls) in it. There may be a list of the worksheets and ThisWorkbook under it. If not, click the + next to your project, then expand Microsoft Excel Objects the same way.
Now double-click ThisWorkbook and copy the following into the main window:
Private Sub Workbook_Open()
Application.DisplayFormulaBar = True
End Sub
Private Sub Workbook_BeforeClose(Cancel As Boolean)
Application.DisplayFormulaBar = False
End Sub
Alt F11 to return to your spreadsheets, then save your work.