Copying from one workbook to another

Hi,

I have three different workbooks with some data which is dynamic in the sense that the no. of rows of data will keep on changing in these workbooks.
How do I link all these to a new 4th workbook which will summarise the data from all these workbooks one below the other and adjust according to the no. of rows in each original workbook?

Eg. WORKBOOK 1 Worbook 2 Workbook 3
a, c f
b d g
e h



I want the fourth workbook with a to h one below the other and since data in workbooks 1,2, and 3, will keep on changing (they might have more or less rows)
the Workbook 4 should automatically get updated.

Is this possible?