Assuming you are referring to the View as: Calendar on the Income & Transfers view on the Bill & Income tab, if the DivX is to the checking account that shows the cash of the investment account, all you should need is an income reminder: select Add > Income Reminder, enter a name for the source, select Next, select the investment account that will receive the dividend from the To account: pull-down menu and Dividend from the pull-down menu that should appear just to the right of the To account: pull-down menu when a investment account is selected, fill out the remainder of the form, and select Done.
If the investment account is not set up to show cash in the checking account, you may select the destination account when the income reminder is entered into the investment register or, instead of an income reminder, you could use a memorized investment transaction in a scheduled transaction group but neither of these approaches alone will allow you to project the cash balance of the checking account. If the projection of the checking account balance is desired, I suggest including transfer reminder which you may use with a Div instead of a DivX or you may ignore (aka skip).