lookupvalue without a RANK or better

[gmazza76]

Good Afternoon,

I am wondering if its possible to use a lookupvalue as per below with a difference

ISU - where all letter date is
refidc - specific ref id


currently using
=LOOKUPVALUE(ISU[issue_date],ISU[refidc],Cancellations[refidc],ISU[letterid],"LetterName",ISU[issue_date],Cancellations[datetocheck])

this pulls the correct information through as long as the [datetocheck] & ISU[issue_date] are a match.
Is there anyway I can pull details through if the [datetocheck] is after the [Issue_date] say within 5 days.

I know I can do something like this in Excel with the if function, but I have no idea with power BI

thanks in advance

Gavin