TCanvas *C;
TPad *p1, *p2;
TH1F *h1, *h2, *h3;

void globalzoom() {
	int first = h3->GetXaxis()->GetFirst();
	int last  = h3->GetXaxis()->GetLast();

	h1->GetXaxis()->SetRange(first, last);
	h2->GetXaxis()->SetRange(first, last);
	
	p1->Modified();  
	p2->Modified(); 
}

void zoomdiv() {
	TCanvas *C = new TCanvas("C", "C", 500, 900);
	C->Divide(1,3,0,0);

	h1 = new TH1F("h1", "h1", 100, -5., 5.) ; h1->FillRandom("gaus", 10000);
	h2 = new TH1F("h2", "h2", 100, -5., 5.) ; h2->FillRandom("gaus", 10000);
	h3 = new TH1F("h3", "h3", 100, -5., 5.) ; h3->FillRandom("gaus", 10000);

	TExec *zoom = new TExec("zoom","globalzoom();");

	p1 = (TPad*)C->cd(1); h1->Draw();
	p2 = (TPad*)C->cd(2); h2->Draw();
	C->cd(3); h3->Draw(); zoom->Draw();
}