I cannot guess, what "gui1.callThisBeforeClosingFcn()" should be. Perhaops you want to call a function before closing the figure autoamtically? But what might "from another GUI" mean then...
figure('CloseRequestFcn', @callThisBeforeClosingFcn, ...
'DeleteFcn', @callThisBeforeClosingFcn);
and your function:
function callThisBeforeClosingFcn(FigH, EventData)
handles = guidata(FigH);
... do whatever you want
figure('CloseRequestFcn', [], ...
'DeleteFcn', []);
delete(figure);
Now simply close or delete the figure, or close it using the "x" in the window border and the specified function is called automatically.
