Not sure what error this is

[gemma-the-husky]

You need to change the line

Price = Nz(DLookup([Price], [OrderDetailsQ], "ProductDetailsID=" & Me.ProductCmb), 0)

in the following

Price = Nz(DLookup("[Price]", "[OrderDetailsQ]", "ProductDetailsID=" & Me.ProductCmb), 0)

I'm not sure but you might also need spaces before and after the equals sign in these expressions. I probably add spaces in SQL expressions where I don't need them, but I know for sure there are some places where you do need to have them.