Returns or sets a String indicating the validation formula for the user property. Read/write.
expression.ValidationFormula
expression Required. An expression that returns a UserProperty object.
Example
The following Visual Basic for Applications (VBA) example demonstrates the use of ValidationText and ValidationFormula properties.
Sub TestValidation()
Dim outApp As New Outlook.Application
Dim tki As Outlook.TaskItem
Dim uprs As Outlook.UserProperties
Dim upr As Outlook.UserProperty
Set tki = outApp.CreateItem(olTaskItem)
tki.Subject = "Work hours"
tki.TotalWork = 3000
Set uprs = tki.UserProperties
Set upr = uprs.Add("TotalWork", olFormula)
upr.Formula = "[Total Work]"
upr.ValidationFormula = ">= 2400"
upr.ValidationText = """The WorkHours (Total Work) should be equal or greater than 5 days """
tki.Save
tki.Display
MsgBox "The Work Hours are: " & upr.Value
End Sub