Userform that allows user to select an open file?

wouldnt it be wise just to open the file with Open dialog?
Of course you can browse workbooks collection (contains all open wbks in this instance of excel).
something like

dim wbk as excel.workbook
for each wbk in application.workbooks
  if wbk.name <> thisworkbook.name then
  ' populate some control in Userform like list.add or something
   ' or check some characteristic sign that "this is the file" an if "it is -> exit for
  end if
next wbk

Originally Posted by Kaper

wouldnt it be wise just to open the file with Open dialog?
Of course you can browse workbooks collection (contains all open wbks in this instance of excel).
something like

dim wbk as excel.workbook
for each wbk in application.workbooks
  if wbk.name <> thisworkbook.name then
  ' populate some control in Userform like list.add or something
   ' or check some characteristic sign that "this is the file" an if "it is -> exit for
  end if
next wbk

Thanks! That would work too. Is there a way to open a file and then have it copy in data even if I don't know the name of that document (since it will change every day)? I just want to push a button, and have it copy in data. So whatever method is the easiest works.

Let's make it with small steps - here is a proposition of a framework for you. Create a button and assign the macro mytestmacro to it:
First test it and then

Sub mytestmacro()
Dim FileName As Variant
Dim SourceFile as Workbook, MainFile as workbook : Set MainFile=ThisWorkbook

FileName = Application.GetOpenFilename(filefilter:="Excel files (*.xls*),*.xls*", FilterIndex:=3, Title:="Choose a file")
If FileName = False Then  
   MsgBox "No file selected!", vbcritical
   Exit Sub
else
   Set SourceFile = Workbooks.Open(Filename)
   ' and here your processing, for instance
   SourceFile.Sheets(1).Range("A1:D5").copy MAinFile.Sheets(1).cells(rows.count,"A").end(xlup).offset(1,0)
   ' then close file and let user (you) know it is finished
   sourcefile.close false
   msgbox "finished copying from " & Filename      
end if
End Sub

if it works adjust the copying part:

   SourceFile.Sheets(1).Range("A1:D5").copy MAinFile.Sheets(1).cells(rows.count,"A").end(xlup).offset(1,0)

to copy from and to right places in your workbooks (as it is now it copies from Sheet1!A1:D5 of newly open file to first blank cell in A column in Sheet1 in your main file.