In Continuous or Design View forms, such as the one in your attachment, most conditional formatting cannot be done thru code. The reason for this is that while you think you have multiple "Genomen" textboxes, you have, in fact, multiple instances of a single textbox, and any formatting you apply to it will be applied to all instances for the textbox. In other words, if "Genomen" is invisible in one record it will be invisible in all records!
Trevor's type of code can only be used in Single View Forms.
To do Conditional Formatting in Continuous or Design View forms, you have to use CF from the Format menu.
Unfortunately, using CF from the menu does not include setting the visibility/invisibility of controls. The closest to this that you could do would be to set the Back Color and Fore Color to the same color if a condition exists.