Subsref error (Index exceeds matrix dimensions)

function [VarNames] = TimeAlignMatFile(InputFilename,DeltaTime) % option to evaluate variables across longest time range recorded use_full_time_range = 1;

    DataStructure = load(InputFilename);
    Names = fieldnames(DataStructure);
    NoNames = length(Names);
    VarNames = (Names(2:NoNames));                  % Names(1) is always 'header', so ignore

    % Create individual structure for first variable in the MAT file
    Part.type = '()';
    Part.subs = Names(2);
    TempStructure = subsref(DataStructure, Part);
    time = TempStructure.time;