a macro to find text based on user input

If you want to go with just opening the find dialogue programmatically then ABabeNChrist's code is the one to use, but you'll have to enclose it in a sub-routine, e.g.

Sub OpenFindBox

ActiveWindow.SelectedSheets.Application.Dialogs(xlDialogFormulaFind).Show

End Sub

Of course now the issue is that you need some way of launching that ... some way even easier than just pressing CTRL-F. It can be set to open when the workbook is opened, or when the user changes the value of a certain cell, or a host of other options - what's your requirement here?