I have a custom function in Excel
I want to run other sub lets say to display a msg box each time the
function
is used in the sheet (not each time the function is calculated)
ie. only at the time the function is used in the sheet.
lets say in coding i want the following

Function myfunction (x as variant) as variant
myfunction = x+x
end function

sub mysub ()
'this should run each time the function
'my function is used in the cell
'not each time the function is calculated
msgbox "Myfunction is used in the active cell"
end sub