SUMIF - but including only items with certain characters included

I can easily use SUMIF() to get totals based on the contents of cells in a column, but is there any way to do the same to add up, for example, only the cells that include the character "I" (or any other character) anywhere in the string?

e.g.
817001 - I - 16/07/14 (include this)
3567777 23/6/14 (exclude this)
235555 I 22/7/14 (include this)

I know I can use the FIND function to look at each cell, but this would mean adding in an extra column to store the answer I need to use for the adding up. It's not my file and is live so I don't want to do that.

Any ideas? Thanks.

Hi,

Thanks, I'm trying to do this without having an extra column. There are a number of ways I could do it with the extra column to store either the find results or the values for adding up. I don't want to change the format of the file being used at all as it is not mine and is live. The figure worked out will go into my own separate summary file without changing the original file. I need to be able to update regularly so I wouldn't want to just copy the file each time to work out the amount.

Thanks