From userform, open file and run macro

I have a userform which begins with a "Find File" button.
Once the user has found the excel sheet he wishes to use (which has a macro on it that does a specific thing) the "Find File" macro opens the worksheet. Once this is done, how can I set it to run the macro on that newly opened worksheet?

Private Sub CommandButton1_Click()
ChDrive "D:\"
ChDir "D:\Documents"
FileToOpen = Application.GetOpenFilename _
(Title:="Please choose a file to import", _
FileFilter:="Excel Files *.xls (*.xls),")

If FileToOpen = False Then
MsgBox "No file specified. You must select a file for the macro to run", vbExclamation, "Error"
Exit Sub
Else
Workbooks.Open Filename:=FileToOpen
End If

End Sub

I dont know if i can set a Dim or something to do this or also if i need to set the specific macro name but assume the macro name is macro1 if that is the case

Thanks,
Penfold