Reminders and Buying Shares

When I am in a checking account I can record a purchase of shares of a specific mutual fund; e.g., BuyXfr, Joe's Mutual Fund, Dingbat Fund, and type in the shares, and amount.

I can't do this when setting up a reminder. In the reminders I can set up to transfer money to Joe's Fund, but I can't set it to buy the actual fund type; e.g., Dingbat Fund. Basically;y, as a reminder it appears to force you to use a cash account in the mutual fund, but then there is no easy way that I can see to move money from the cash account to the actual fund,