Hi @Yaro
I've written a vbscript to read all the open workbooks and display it in a Listbox.

Copy paste the below code in a blank Flow editor and test the Flow.
Scripting.RunVBScript VBScriptCode: $'''Dim wkb, objXL
On error resume next
Set objXL = GetObject (, \"Excel.Application\")
For Each wkb In objXL.Workbooks
strMessage = strMessage & wkb.FullName & \"|\"
Next
set objXL = nothing
Wscript.Echo strMessage''' ScriptOutput=> VBScriptOutput
Text.SplitText.SplitWithDelimiter Text: VBScriptOutput CustomDelimiter: $'''|''' IsRegEx: False Result=> TextList
Variables.RemoveItemFromList.RemoveItemFromListByIndex ItemIndex: TextList.Count - 1 List: TextList
Display.SelectFromListDialog.SelectFromList Title: $'''Excel File selection''' Message: $'''Please select a file''' List: TextList IsTopMost: False AllowEmpty: False SelectedItem=> SelectedItem SelectedIndex=> SelectedIndex ButtonPressed=> ButtonPressed
The user still has a chance to select an incorrect file if more than one are already opened but I believe this is what you wanted.
You need to add your own validation for scenarios where no Excel files are already opened on the system.