Update a cell in one workbook whenever a cell from another workbook is updated

[Maddoktor]

Hi all,

My problem is as follows:

In column A (main workbook) I have a cell that needs to be updated according
to the date entered into a column in another (secondary) workbook. The catch
is that the other (secondary) worksheet (the column where the date is
entered) is forever growing and I would like for the cell in column A of the
main workbook to change (a calculation needs to be done) according based on
the dated entered into the secondary workbook. Once the date in the
secondary workbook matches a specific cell in the original workbook then the
particular cell in column A should stop updating.

Is this possible???