Drawing a GUI.DrawTexture call above GUI.Button in seperate scripts

I have a script w$$anonymous$$ch controls my main menu functionality w$$anonymous$$ch in OnGUI() draws multiple GUI.Buttons. Clicking each button begins a separate loading screen script w$$anonymous$$ch in OnGUI() calls GUI.DrawTexture and draws a black texture rectangle w$$anonymous$$ch covers the entire screen. I need t$$anonymous$$s black texture to be on top of the buttons w$$anonymous$$ch are being drawn from a different script.

I have tried altering the depths of both separate OnGUI() calls before realising that the depth is dependant on the separate OnGUI() calls. I have also tried to adjust the script execution order and placing the loading screen script so it executes later.

Is there an alternative way to control the depth of GUI components between different scripts?