A good IF statement is like a good hound dog--just give him a sniff o' what he needs to find and turn him loose to find the trail!
Today's topic is something I use literally every day: IF statements whose behavior is driven by looking for certain text strings. There are COUNTLESS uses of this thing, but a very common one is cleaning long lists of hyperlinks, some of which have the "http://" and some don't.
In English first, we want our IF statement to do the following:
"If I can't find 'http://' in the string, concatenate 'http://' with the string; otherwise, just leave the text string unchanged"
Excel-speak for "can't find" is a combination of two formulas: ISERROR and FIND.
When the FIND function doesn't find it's target, it generates an error--so putting that inside an ISERROR gives us the TRUE/FALSE we need to power our IF statement.