Dynamic month year in if vlookup

hi guys,
I want to extract some columns from recently downloaded file its format is like ABC_Report_ZFI_CAPI_MNO_Aug-21_Summary.xlsx basically Aug-21 is dynamic it will change every month so i used if Formula in vlookup so for dynamic date what we need to do


Do the month is current month or will be the previous month?

Replace “Aug-21” with