I am not sure I understand your question. Do you want to simply control where the cursor is on the picture you are appending to the html report. If so then when you use the Append Control Image to Report VI it basically takes a snap shot at that moment and displays it. Therefore you just need to place the cursor where you wnat it before you add the image.
To programttically control the cursor you will need to use property nodes of the Waveform Graph. A good start would be the property cursor>>cursor position>>all elements.