Help with formula for minimum date

[squnibi]

I have two columns: in one column i need to find the beginning date and in the other column i need to find the ending date.

Beginning Date Formula:

=IF(A2="","",eomonth(MIN(OFFSET(PortfolioData!$A$1,MATCH(port1,PortfolioData!$B:$B,0)-1,,COUNTIF(PortfolioData!$B:$B,port1),1)),-1))


Ending Date Formula:
=IF(A2="","",eomonth(MAX(OFFSET(PortfolioData!$A$1,MATCH(A2,PortfolioData!$B:$B,0)-1,,COUNTIF(PortfolioData!$B:$B,A2),1)),1))


Can someone explain why this is resulting in a #NUM error?

I appreciate any help