{=AVERAGE(N(OFFSET(A13,
,LARGE((G13:IV13<"")*(COLUMN(INDIRECT("G:IV"))),{ 1,2,3,4})-1,1,1)))}

That's the formula that I'm working with. As the subject says, I need
a way for it to display a dash in the cell and not the #REF error. Is
there anyone out there that can help me out?

P.S. I didn't write the formula to begin with and know next to nothing
about excel