The code below will allow you to set the Startup properties.
The property has to be created before it can be set, but it can be set as it is created (if you see what i mean).
But as I said before you have to close the file and re-open for a change to take effect.
Usage:
CreateProps 3
The final 0 for each statement can be 0 or 1 depending on whether you are unsetting or setting the option.
Sub createprops(x)
Dim prp As DAO.Property
Dim db As Database
Set db = CurrentDb()
Select Case x
Case 1
Set prp = db.CreateProperty("StartUpShowDBWindow", 1, 0)
db.Properties.Append prp
Case 2
Set prp = db.CreateProperty("AllowBreakIntoCode", 1, 0)
db.Properties.Append prp
Case 3
Set prp = db.CreateProperty("AllowSpecialKeys", 1, 0)
db.Properties.Append prp
Case 4
Set prp = db.CreateProperty("AllowToolbarChanges", 1, 0)
db.Properties.Append prp
Case 5
Set prp = db.CreateProperty("AllowFullMenus", 1, 0)
db.Properties.Append prp
Case 6
Set prp = db.CreateProperty("AllowBuiltInToolbars", 1, 0)
db.Properties.Append prp
Case 7
Set prp = db.CreateProperty("AllowByPassKey", 1, 0)
db.Properties.Append prp
Case Else
'do nothing
End Select
End Sub