How do I send a "hold xbutton down for x time"?

I'm trying to automate something and I need to have it press RSHIFT and then Right mouseclick, I already have the window stuff setup but putting
Send("{RSHIFT}")
MouseClick( "Right", 1110, 435, 1, 1)

The shift button needs to be held down so that when right mouseclick happens then its like rshift+mouseright.
Because the GUI shows a seperate menu when you press Shift. So a hold shift till x time would work.