Close Multiple Workbooks

How can I close the currentmonthend AND previousmonthend workbooks in the following code, but leave workbook "MoEnd Compare" open? I'd like to do some additional comparisons with the "MoEnd Compare" file. I tried the code below to close those two workbooks, but it is not working.

Sub check_month_end()
Dim currentmonthend
Dim previousmonthend
Dim project_current
Dim ptcurrent
Dim yearcurrent
Dim project_previous
Dim ptprevious
Dim yearprevious
Dim r As Integer
Dim c As Integer
Dim l As Integer
MsgBox "This will check project type and year on current and last period month end report."
currentmonthend = Application. GetOpenFilename("Excel Files (*.xls),*.xls", , "Select CURRENT Month End Report?")
previousmonthend = Application.GetOpenFilename("Excel Files (*.xls),*.xls", , "Select PREVIOUS Month End Report?").......................