A family of Microsoft relational database management systems designed for ease of use.
This form searches for a check number in another form. If it exists, it opens that form.
Forms DISPLAY data they don't hold data. So, if you want to search for the existence of data you search through a table, not a form. If the form uses a filtered Recordsource, then you search through that Recordsource.
I see Ken suggested some better coding that you got to work. But you do need to understand how it works.