Check if exist (W/Out taking the extension)

I'm not sure if I phrase this correctly, but is it possible to have autoit check if test.txt exist on desktop if I only type "Test" on input instead of "Test.txt"?

I tried:

If FileExists(GuiCtrlRead($input1 & ".txt")) Then   ;Check if exist;
NewFunction()                ;Else execute New Function;
Else
MsgBox(0, "File Exist", "Exported Job Does Not Exist!!!")
EndIf

When try this medthod; I get the msgbox that Job does not exist.