is it possible to program to conditionally format a variable range of cells?

would like to look at values in column a...if criteria are met, then apply
conditional formatting to the cell in column g...where the conditional
formatting references only the cells in column g where the formatting is
applied.

for example, column a is group name and column g is total tasks completed.

if cells a4, a9, and a13 meet the criteria (e.g. group names specified in
the macro), then conditional formatting is applied to cells g4, g9, and g13
where the conditional formatting that is applied refences g4, g9, and g13 so
as to find highlight the cell with the maximum tasks completed for only these
three cells.