If I have understood correctly, the code below may get you started:
Names Default To Here( 1 );
// Skeleton Table
dt = New Table( "User Supplied Values",
Add Rows( 0 ),
New Column( "Minumum", Numeric, "Continuous", ),
New Column( "Target", Numeric, "Continuous", ),
New Column( "Maximum", Numeric, "Continuous", )
);
// Make a UI to allow the values to be entered
cols = dt << getColumnNames( "String", Continuous );
lub1 = Lineup Box( N Col( 1 ) );
lub2 = Lineup Box( N Col( 1 ) );
For( c = 1, c <= N Items( cols ), c++,
lub1 << Append( Text Box( cols[c] ) );
lub2 << Append( Number Edit Box( . ) );
);
nw = New Window( "Enter Values",
<<onClose( makeGraph ),
Lineup Box( N Col( 2 ), lub1, lub2 ),
Lineup Box( N Col( 2 ), Button Box( "Add", addScript ), Button Box( "Cancel", nw << closeWindow ) )
);
// Add a new row to dt when required
addScript = Expr(
dt << addRows( 1 );
lastRow = N Row( dt );
For( c = 1, c <= N Items( cols ), c++,
Column( dt, c )[lastRow] = (lub2[c] << get);
lub2[c] << set( . );
);
);
// Make a graph
makeGraph = Expr(
If( N Row( dt ) > 0,
Beep();
Print("Insert code here.")
);
);