Easiest way to link cells in different spreadsheets?

I have two spreadsheets. A cell in one of them needs to contain the same dollar amount as a cell in the other one and to be automatically updated when the first one changes. I’ve tried the instructions in the Help file but they don’t seem to work. What is the easiest way to establish this link?

Once a link is established between spreadsheets it appears that the link will not be updated unless a) the source spreadsheet is saved and b) either the target spreadsheet is set to update automatically (with a time that can be specified) or the target spreadsheet is closed and reopened and the Update Links question answered affirmatively or the link is updated manually.

We cannot get a link to alter in another spreadshet when we alter the original cell which is linked to it