How to extract text from excel column : [{"task":"Start","started":0},{"task":"security-oauth2-validate","started":27},{"task":"EncryptClientId.xsl","started":31},{"task":"set HTTP Header","started":70},{"task":"switch","started":74},{"task":"validate GetMemberRequest","started":77},{"task":"invoke MBEv2 REST Interface","started":94},{"task":"DashboardLogging.js","started":468},{"task":"set http header","started":508},{"task":"catch","started":513}]

I have rows containing text similar to the above.

I would like to find the result of 468-94 = 374 

Note : 468 is the value of started field for "DashboardLogging.js"
Note : 94 is the value of started field for "invoke MBEv2 REST Interface"


Could someone please let me know how this can be achieved in excel . 