diff --git a/Projects/AlPhaPha/2024/macro/mwpc/HistoPosFiller.cxx b/Projects/AlPhaPha/2024/macro/mwpc/HistoPosFiller.cxx
index 2a3958f462f6d1d775a0ba1a9c9d7e96366d0dde..917f24954759d57d005be229f27282caa2182797 100644
--- a/Projects/AlPhaPha/2024/macro/mwpc/HistoPosFiller.cxx
+++ b/Projects/AlPhaPha/2024/macro/mwpc/HistoPosFiller.cxx
@@ -1,6 +1,6 @@
 #include <vector> // Needed to store histograms.
 
-void HistoPosFiller(int RunStart, int RunStop) {
+void HistoPosFiller(const char* FileName) {
   // **************************************************************************
   // This macro simply fill an histogram per FPMW and store them in a root file.
   // It is needed for the input of the LinearisationYaml.cxx macro.
@@ -22,9 +22,8 @@ void HistoPosFiller(int RunStart, int RunStop) {
 
   // Import the chain
   TChain *ch = new TChain("PhysicsTree");
-  for (int run = RunStart; run <= RunStop; run++) {
-    ch->Add(Form("../../root/analysis/linea_%d.root", run));
-  } // End of run loop
+  ch->Add(Form("../../root/analysis/%s.root", FileName));
+  // End of run loop
 
   // Declaration of the histograms storing the reconstructed position
   vector<TH1F *> Position;
diff --git a/Projects/AlPhaPha/2024/macro/mwpc/ReadMe.md b/Projects/AlPhaPha/2024/macro/mwpc/ReadMe.md
index fef5c6360b8b24e0b22126cd85ec6359a8ade8a2..d3e366aa699ba62eb356485a90f84346cc6d50d1 100644
--- a/Projects/AlPhaPha/2024/macro/mwpc/ReadMe.md
+++ b/Projects/AlPhaPha/2024/macro/mwpc/ReadMe.md
@@ -9,9 +9,7 @@ First thing first you need a run filled with a good amount of data with the
 position on the FPMW unlinearised. 
 
 Then execute the HistoPosFiller.cxx macro with the following command in terminal
-: root 'HistoPosFiller.cxx(RunStart,RunEnd)'
-
-The run you are using should have a name of the form : linea_$RunNumber$.root
+: root 'HistoPosFiller.cxx(FileName)'
 
 This macro will fill the histogram with the unlinearised FPMW position and store them in the HistUnlinea.root file. It is mandatory to run the following steps.