I haven't heard any IDE that supports your request, but you can do this in BASH(bourne-again shell) easily.
Assuming that your source code files are all *.cs:
ls *.cs | while read a
do
sed -i.bak 's/Picture\([0-9]*\)_75/picBox\1/g' $a
done
I recommend you to look at sed utility which is very useful in text processing.
Another point, if you like to search for *.cs files in a directory and its sub-directories, better to use
find . -name "*.cs"
instead of "ls *.cs".
Life is easier with shell scripting :)