LinuxQuestions.org - sed, negate and variable

Hey!
I'm trying to use sed to search through a text, and replace a variable containing spaces with 'bar'.
But i don't want to replace on lines containing 'foo'.
The reason i want to use a variable is that the sed-command is in a for-loop, so it get's a different variable each loop.

It works when i want to replace on lines with foo:

Code:

$ echo ${test}

test1 test2

$ echo ${test// /\\ }

test1\ test2

$ cat file

test1

test2

replace this test1 test2

don't replace when foo test1 test2

$ sed "/foo/s/${test// /\\ }/bar/g" file

test1

test2

replace this test1 test2

don't replace when foo bar

But when i want to negate lines, bash freaks out.

Code:

$ sed "/foo/!s/${test// /\\ }/bar/g" file

bash: !s/${test//: event not found

Also, this works of course:

Code:

$ sed '/foo/!s/test1\ test2/bar/g' file

test1

test2

replace this bar

don't replace when foo test1 test2

But i have to use double quotes for sed to understand my variable.
Otherwise i get:

Code:

$ sed '/foo/s/${test// /\\ }/bar/g' file

sed: -e expression #1, char 17: unknown option to `s'

So, can i negate the regular expression foo without using !
Or can i use sed-branching to test if the regexp foo is not on a line?
Or does anyone have a good hint on how to achieve this? Thanks!