Use the Worksheet Change event of the applicable worksheet. Right
click on the sheet tab and select View Code. Then place something
like below.

This will maximize the Excel application when range D5 = 6. Adjust as
needed.
Private Sub Worksheet_Change(ByVal Target As Range)
If Cells(5, 4).Text = "6" Then _
Application.WindowState = xlMaximized
End Sub

Mike wrote:
Is it possible for Excel to maximize automatically when a certain value is
triggered in one of the cells with a formula? ie. If I have a spreadsheet
linked to a live quaote system and I want excel to auto maximize as soon as a
certain number is hit in a cell?

Thanks