One way:
Option Explicit
Sub testme01()
Dim mySuggestedFileName As String
Dim myFileName As Variant
With Worksheets("sheet1")
mySuggestedFileName = "c:\my documents\excel\test\" _
& Format(.Range("a1").Value, "yyyy_mm_dd") & ".xls"
End With
myFileName = Application.GetSaveAsFilename _
(InitialFileName:=mySuggestedFileName, _
filefilter:="Excel File,*.xls")
If myFileName = False Then
MsgBox "try Later"
Exit Sub
Else
Application.DisplayAlerts = False 'no warning for overwriting
ThisWorkbook.SaveAs Filename:=myFileName, FileFormat:=xlWorkbookNormal
Application.DisplayAlerts = True
End If
End Sub