"Invalid use of null" for OpenArgs when calling OpenForm - vba

Question

I cannot find the reason but I keep getting an invalid use of null when using OpenArgs
The code is set up with
Private Sub cmdContactDetails_Click()
Dim ArgsString As String
ArgsString = Forms!LeadList![Entrepreneur Name] & "," & Forms!LeadList![Telephone Number] & "," & Forms!LeadList![Email Address]
DoCmd.OpenForm "ContactDetails", , , , , , ArgsString
End Sub
This results in the string "X,123456789,test#test"
In the Form_Open event of contact details I have:
Dim SaveString As String
SaveString = Forms!ContactDetails.OpenArgs
But this gives me an "Invalid Use of Null" message even though nothing is null.

Answer 1

Assuming you have a form named:- "LeadList"
and the form also has a text box named:- "Entrepreneur_Name"
and this form contains the following code:-
Option Compare Database
Option Explicit
Private Sub cmdContactDetails_Click()
Dim ArgsString As String
ArgsString = Me.Entrepreneur_Name
DoCmd.OpenForm "ContactDetails", , , , , , ArgsString
End Sub
The above code is called via a command button named "cmdContactDetails" on the form named:- "LeadList" then the form "ContactDetails" will be opened (form "ContactDetails" must be closed first) and the on open event will run this code:-
Option Compare Database
Option Explicit
Private Sub Form_Open(Cancel As Integer)
Dim SaveString As String
SaveString = Forms!ContactDetails.OpenArgs
MsgBox " >>> " & SaveString
End Sub
The message box will display the contents of the text transferred via the open args function from the form "LeadList" text box "Entrepreneur_Name"