2000 doesn't support trigger animations so your only option is vba.
Do you have any coding skills?
I don't have 2000 so I am not sure it supports this code but you could try this macro
Code:
Sub swell(oshp As Shape)
If oshp.Width < ActivePresentation.PageSetup.SlideWidth Then
SaveSetting "SIZE", "SETTING", "LEFT", CStr(oshp.Left)
SaveSetting "SIZE", "SETTING", "TOP", CStr(oshp.Top)
SaveSetting "SIZE", "SETTING", "WIDTH", CStr(oshp.Width)
SaveSetting "SIZE", "SETTING", "HEIGHT", CStr(oshp.Height)
oshp.Width = ActivePresentation.PageSetup.SlideWidth
oshp.Height = ActivePresentation.PageSetup.SlideHeight
oshp.Left = 0
oshp.Top = 0
oshp.TextFrame.TextRange.Font.Size = 4 * oshp.TextFrame.TextRange.Font.Size
Else
oshp.Width = GetSetting("SIZE", "SETTING", "WIDTH", "100")
oshp.Height = GetSetting("SIZE", "SETTING", "HEIGHT", "100")
oshp.Left = GetSetting("SIZE", "SETTING", "LEFT", "0")
oshp.Top = GetSetting("SIZE", "SETTING", "TOP", "0")
oshp.TextFrame.TextRange.Font.Size = oshp.TextFrame.TextRange.Font.Size / 4
End If
End Sub