Rather than explicity calling the btnSaveTransaction_Click(objSender, e) method directly you might want to use the PerformClick on the btnSaveTransaction2 control.
Also I notice you are creating a lot of controls in the code i.e.
Dim ctlDateTimePicker As New DateTimePicker, ctlComboBox As New ComboBox, ctlTextBox As New TextBox
Dim ctlCheckBox1 As New CheckBox, ctlCheckBox2 As New CheckBox
if you are going to assign existing controls to these variables you do not need the New keyword - this will prevent you creating the unused instances of the controls and will keep the memory utilisation down.
In the line
Dim objSender As Object = DirectCast(Me.Controls("btnSaveTransaction2"), Object)
the direct cast isn't required as everything is an object and therefore the cast is always safe and going to succeed.
In the long run though it might be easier to have two separate methods - one to update the transactions table and one to update the transactions_weekly table and simply call the correct method(s) from the appropriate button click event.