Copying data without opening workbook using Excel VBA - vba

Question

I'm intending to copy data from one workbook to another through a macro. However, I'm using an Add-In my company has created, which prohibits more than one workbook to be open at once.
Application.ScreenUpdating = False
CurrentYear = Year(Date)
CurrentMonth = Month(Date)
StartDate = DateAdd("m", MonthOffset, Date)
MonthNo = Month(StartDate)
YearNo = Year(StartDate)
path2 = IIf(MonthNo >= 10, Dir("C:\path\filename " & YearNo & "-" & MonthNo & ".xlsx"), Dir("C:\path\filename " & YearNo & "-0" & MonthNo & ".xlsx"))
p2file = "C:\path"
Varrr = IIf(MonthNo >= 10, p2file & path2 & "[filename.xlsx " & YearNo & "-" & MonthNo & ".xlsx]Sheetname!", p2file & path2 & "[filename.xlsx " & YearNo & "-" & MonthNo & ".xlsx]Sheetname!")
i = 0
Do While Len(path2) > 0
Varrrcell = Cells(3,4+i).Address(RowAbsolute:=False, ColumnAbsolute:=False)
Varrr = Varrr & Varrrcell
currentWb.Sheets("Blad1").Cells(27, 2 + i + 12 * (YearNo Mod 2015)).Formula= "=Varrr"
i = IIf(i > 12, 1, i + 1)
YearNo = IIf(i > 12, YearNo + 1, YearNo)
path2 = IIf(i >= 10, Dir("C:\path\filename " & YearNo & "-" & i & ".xlsx"), Dir("C:\path\filename" & YearNo & "-0" & i & ".xlsx"))
Varrr = IIf(i >= 10, p2file & path2 & "[filename.xlsx " & YearNo & "-" & MonthNo & ".xlsx]Sheetname!", p2file & path2 & "[filename.xlsx " & YearNo & "-" & MonthNo & ".xlsx]Sheetname!")
Loop
Application.ScreenUpdating = True
EDIT: I've recoded my work to reference to the workbook directly using formula. This solution actually returns the correct path, file and cell I want to copy so that works as intended. However, it returns "Varrr" in each cell. How can I make it return the value instead of the variable name?
EDIT2: I've also contatenated "='" before path2 & p2file & ".." when creating and updating Varrr, and simply saying that
currentWb.Sheets("Blad1").Cells(27, 2 + i + 12 * (YearNo Mod 2015)).Formula= Varrr
but this causes error 1004
EDIT3: I've also added a "closing" ' before the name of the sheet. It did not help.
EDIT4: I've also tried to omit the equal signs, and contenated Varrr = Varrr & Varrcell
and subsequentially put:
currentWb.Sheets("Blad1").Cells(27, 2 + i + 12 * (YearNo Mod 2015)).Formula = "=" & varrr
but it gives code 1004 in the same code snippet. "Application-defined or Object-defined error"
EDIT 5:
Trying to incorporate ExecuteExcel4Macro I've tried the following solution, where Dim ReturnedValue as String:
Varrr = "'" & p2file & "[filename.xlsx " & YearNo & "-" & MonthNo & ".xlsx]Sheetname!'"
ReturnedValue = Varrr & Range("D3").Adress(True,True,-4150)
MsgBox ExecuteExcel4Macro(ReturnedValue)
where the MsgBox gives function error 1004. Here I have trimmed it down a bit to omit the "IIf" statement and the Do loop as I Believe these are redundant in the context.