the quickest way to achieve what you're after is to use the FIND
function to search the text, which will return an error if it can't
find the relevant text. You can then use the ISERROR function with a
'--' infront to return ones and zeros which you can simply add up. You
will need to enter this as an array formula (hold ctrl+shift whilst
pressing enter).
So an example might be:
=SUM(--ISERROR(FIND("foobar",A1:A5)))
Rob