I have a summary in Book1, which I would like to transfer to Book2.
Does anybody has the proper formula? Thanks!

The following is from Microsoft Excel Help (look up "Create a link to another cell":

1) Open both the workbook that will contain the link (called the destination workbook), and the workbook that contains the data you want to link to (called the source workbook).

2) In the destination workbook, click Save .

3) Select a cell or cells you want to link from.

4) If you are creating a new formula, type = (an equal sign).

5) If you are entering the link elsewhere in the formula, type the operator or function that you want to precede the link.

6) On the Window menu, click the name of the source workbook, and then click the worksheet that contains the cells you want to link to.

7) Select the cells you want to link to.

8) Complete the formula. When you finish entering the formula, press ENTER.

So if I have two workbooks, "workbook1.xls" and "workbook2.xls" and workbook2 contains the value "abc" and I want to link that value to workbook1, the resulting formula in workbook1 will look like:

=[WORKBOOK2.XLS]Sheet1!$A$3

Where "[WORKBOOK2.XLS]" is the source of the data, "Sheet1" is the worksheet within that workbook and "$A$3" is the cell containing the data.