Draw A surface between 2 sinus cuves qwt

[benamiar]

hello guys,
i would love to draw the surface between à two sinus curves. the two sinus curves have the same base of time it mean the x of first point of my two sinus are the same .
so how can i do that? my idea is to draw a bunchs of lines between the 2 sinus points but i didn't find a function in the qwt that allow me to draw lines between two point that have the same x and different y .

if you have a better idea i would love to listen to it .

thanks for your respond guys .

[benamiar]

the grey part is the kind of surface I want to draw