InfoPath Dev

but how ?

Well, there are many ways to do that, but here is how I did it.  First you have to get the value from the field and define it as a string. The red text is the xpath to the field that contains the information that you want to be the subject - yours will be different than mine. 

//Subject

XPathNavigator SubjectField1 = MainDataSource.CreateNavigator().SelectSingleNode("/dfs:myFields/dfs:dataFields/d:Buyers/d:WorkOrders/@WorkOrderType", NamespaceManager);

string SubjectSeed1 = SubjectField1.Value;

Then assign that string to the myAppointment.Subject object like this:

myAppointment.Subject = (SubjectSeed1);

Thank you!

Unfortunaly a error occurt. Run Time Error     |      object demans: 'Main DataSource'

Can you tell me what I am doing wrong?

--- below the code

Sub CTRL59_7_OnClick(eventObj) 

Dim dateIndex, timeIndex, descriptionIndex, duration, reminderTime 
Dim eventDate(), eventTime(), eventDescription(), i 
Dim objOutlook 
Dim myItem 
Dim SubjectField1

Set objOutlook = CreateObject("Outlook.Application") 
Set myItem = objOutlook.CreateItem(1)

SubjectField1 = MainDataSource.CreateNavigator().SelectSingleNode("/dfs:myFields/dfs:dataFields/d:Klanten/@Klantnummer", NamespaceManager) 
string SubjectSeed1 = SubjectField1.Value 

myItem.MeetingStatus = 1 
myItem.Subject = SubjectSeed1 
myItem.Location = "B" 
myItem.Start = #10/1/2009 1:30:00 PM# 
myItem.Duration = 60 
myItem.Send

End Sub