How to use cut or awk commands into sed command ?

[Halid Faith]

I have a file named file1 which contains some values.
I want to replace some strings into it, so I use sed command but I get an error.

sed "s#oldstring#`cut -d, -f3 file2`#"  file1

sed: 1: "s/yenidomain2/f0b2875d- ...": unterminated substitute in regular expression

also I get an error with awk command into sed;
sed "s#oldstring#`awk -F, '{print$3}' file2`#"    file1
sed: 1: "s#yenidomain2#f0b2875d- ...": unterminated substitute in regular expression