Using string variable within Windows().Activate

Hi,
I feel really stupid asking this question but I cannot get this part of my macro to work.

In essence, I am opening one file that contains data that I need to copy to 50 other files (paste special values to the same location in all 50 files).

I open the source file (it is always the same name and located in the same folder).

mfileprs = Cells(mstart, 2) & Cells(mstart, 3)
        Workbooks.Open FileName:=Chr(34) & mfileprs & Chr(34)
        
       Windows("Exchange Rates.xlsx").Activate
        Worksheets("Sheet1").Range("A1:B9").Copy
        
        Windows(mfileprs).Activate
        Worksheets("Rates").Range("AA1:AB9").PasteSpecial Paste:=xlPasteValues

It does not like Windows(mfileprs).Activate but using this same variable to open the file works fine.

What is it that I'm not understanding

This code looks neat but I am getting an error code on the Windows("Exchange Rates.xlsx").........line "Run time error 438: Object doesn't support this property or method". Any clue as to what I need to fix?

Thank you so much xlnitwit, this is super cool and works perfectly. I'm so pleased. You're a star.

Maybe try:

Sub Bozo()
mfileprs = Cells(mstart, 2) & Cells(mstart, 3)
        Workbooks.Open FileName:="ADD YOUR PATH" & mfileprs & ".xlsx"
        ActiveWorkbook.Sheets("Rates").Range("AA1:AB9").Value = Workbooks("Exchange Rates.xlsx").Sheets("Sheet1").Range("A1:B9").Value
End Sub