Using an =IF(ISNA(VLOOKUP formula

I am using an =IF(ISNA(VLOOKUP to check two columns for matching values on any line, returning a yes or no with a match.

Now each value has a simple date on the row also and I want to find the difference in days for the rows returning yes, my issue is I cannot pin point the relating dates as I cannot tell exactly where each yes answer is coming from as all I'm getting back from my first formula is yes/no.

any help would be appreciated

Edit -

=IF(ISNA(VLOOKUP(D2,'Completed installs'!D:D,1,0)),"No","Yes") Returns my yes/no value, I am looking to locate the date on the row of the 'completed installs' !D:D which returned my yes value, for this example the date column is B