excel vba - Need to make vlookup with variable lookup sheet -

i creating vlookup references previous sheet lookup values. tried activecell.formular1c1 = "=vlookup(rc1,sheets(sheets.count - 1)!r1c1:r600c14,11,false)" getting "application or object defined error". sure there way this, struggling figure out.

this untested, think formula being literal way you've written it. try this:

activecell.formular1c1 = "=vlookup(rc1,'" & _     sheets(sheets.count - 1).name & "'!r1c1:r600c14,11,false)"