Compile error: Sub or Function not defined ("SolverOk")

I recorded a macro and then tried to run it.
The macro includes repeated use of the Solver Tool, to save me some time.
Excel does not recognize the "SolverOk" nomenclature (it's highlighted in gray).
I tried checking my References in the VBA editor, but "References" is grayed out so I can't even get into it.

 SolverOk SetCell:="$G$15", MaxMinVal:=3, ValueOf:="0", ByChange:="$G$16"
    SolverSolve