Make the Combobox as an Unbound Combobox, i.e. remove the Control Source property value (MembersID).
Since, you are using only the Unbound Combobox on the Main Form it is not necessary to use tblMembers as Recordsource to the Form.
MembersID field on the tblMembers Table is the PrimaryKey field. When you open the main form, the first record with MembersID value 1 is active. When you attempt to select another MembersID from the Combobox and try to overwrite the PrimaryKey MSAccess prevents that attempt and gives the warning bell. By removing the MemberID field name from the Control Source property of the Combobox corrects this condition.
Besides that set the Default Value Property Value of the Combobox to 1 as well.
Change the VBA statement: Dim rs As Object in your Program to Dim rs As Recordset.
Here's my latest version of form.
It does what I instruct after change in combobx, but I can't navigate through the table.
None of the information change as it relates to action by the navigation bar.
I would like to be able to at least see the records change as they relate to the payments.
I was thinking about adding a text box to the footer of the sform. That would allow me to nav thru subform; subsequently, allow me to id who this list of payments belong to.