Adjust Lookup formula to find first entry

  • I have a lookup formula that finds the last entry and returns the date in that column in the header.

    IFERROR(LOOKUP(2,1/(B2:IM2<>""),$B$1:$IM$1),"")


    How do I adjust it to find the first entry and give me the first date in that column in the header?

  • Will the workbooks be open. This is some code that combines all open workbooks