Hi @scorpio24 ,
Could you please share more details about your scenario? What's the data source of the Gallery, is it the same as of the Form?
Generally speaking, a Form is used for displaying one entry from the data source. Based on your description, you will have three entries, which is incorrect. If you have unique control numbers inside the Gallery, when selecting a number, you can use a Control that allows displaying multiple items, such as Gallery, Data table, ComboBox and ListBox. If you only want to show the accounts relate to selected number, then I suggest you use a Data table Control, set its Items property as below:
Filter(SPlist, 'Control Number' = Gallery.Selected.'Control Number').Account
Best regards,