• Create a Data Log (Project tree ? WinCC ? Logs ? Data logs ? <add new>)
• Create 3 tags (Project tree ? WinCC ? HMI Tags ? Default tag table ? <add new> - in our project, 3 internal tags, HMI_Tag_1 HMI_Tag_2 , HMI_Tag_3 as INT data type)
• Link each tag to the data log (Tags’Loggiin tags tab ? Add new)
• As simulation proposes, attached the created tags to IO fields on a picture (with this it would be possible to input different values to the tags).
• Place on screen the object “Trend Control” (Toolbox ? Controls)
• Configure the Trend Control:
  • Trend areas, [0] trend area, trends, right side, Add new (twice)
  • Trend areas, [0] trend area, trends, [0] trend, data source y, source: link to the logged HMI_Tag_1 log
  • Trend areas, [1] trend area, trends, right side, Add new (twice)
  • Trend areas, [1] trend area, trends, [0] trend, data source y, source: link to the logged HMI_Tag_2 log
• Place a button on the screen.

Hi,

here there is a second example, where, by script, the properties of the trend is changed form other screen.

I suggest take a look at the open related  for FAQ for script, in special chapter 5.4

Screen.FindItem('./Screen window_1/Trend control_1').TrendAreas[0].Trends[0].Visible = 0;