Search for Text within a Range of String, Return IQR of Corresponding Cells

I have been struggling with this formula. I am trying to search for a certain string of text inside a database of larger strings of text, and each time the string is present inside the larger string, I want to put a number corresponding to the text string into the array, and then return the interquartile range of all numbers inside the array.

Simple example:

Assume I am searching for "a:"

sdsasds | 10
fsdss | 24
sawead | 20
ssssss | 28
sddsass | 30
asadaa | 40
jjjjjjj | 23
jaaa | 50

The array would include: 10, 20, 30, 40, and 50, and the inter-quartile range would be 40-20 = 20.

I can piece together parts of the answer:

=PERCENTILE(IF(I$2:I$15="r",B$2:B$15,""),0.75)  -  PERCENTILE(IF(I$2:I$15="r",B$2:B$15,""),0.25)

This would return the interquartile range. It searches Row I and then uses Row B for purposes of forming the array. The problem is that the cells in Column I must be exactly "r" as opposed to merely containing "r."

=IF(FIND("r",I$2:I$15),B$2:B$15,"")

This returns instances of "r" inside any string, but the array attempt does not really work.

I was able to use the following as part of another function:

=SUMIF(Data!M$4:Data!M6551,"*r*",Data!J$4:Data!J$6547)

Thanks for any and all help!