Changing value of a cell based on number input in another

Hi,

I have a spreadsheet where I have the number 1 prepopulated in the cells in column D. I then have values prepopulated in column G.

What I want to be able to do is, if I change the value of a cell in column D to a 2 for example, I want the cell in column G to change to a hyphen. If the value in column D remains as a 1, I want the value in column G to remain as it is.

Can any help me with the forumula? I'm assuming it is some kind of IF formula, however, I've tried a few attempts and either get a non valid name or circular reference.

Thanks