Creating 2D histogram with two seperate file

Newbie
1

I have been plotting a 2D-Histogram and I opened two different file for X and Y axis. How can I fill the plot for two seperate axis at once
‘’'void 2DHistogram()

ULong64_t nEntries = currentAna->GetEntries(); 
cout << "This tree contains " << nEntries << " events!" << endl;
cout << "Loop over " << nEntries << " events!" << endl;
ULong64_t mEntries = current->GetEntries(); 
cout << "This tree contains " << mEntries << " events!" << endl;
cout << "Loop over " << mEntries << " events!" << endl;

‘’’

2

something like that ?

histo2D->fill(x,y,w);