Yes, the idea is to convert a mouse x, y position in pixels to a character cell position of the screen.
So a standard QB64 font is 8 pixels wide and 16 pixels high.
This is why I asked about fonts, they might have different pixel widths and heights for their character cells.
If you stick to print and locate, I think QB64 can match character cells for a custom font. But finding which cell the mouse is over or clicking is crucial for using mouse selection.
So you need a function that converts mouse pixel x, y to column and row of character cell. For such a routine you could input the Font's width and height, the mouse x, y and out comes the cell row, column for locate.
I have a fuller featured array select index function almost ready for much bigger arrays when you need to page through the array of selections but looks like you've got things handled for your application.