You would use the GetObjects command to get an opened version of excel. However, this will take the first opened instance of excel, so if there is more then one version opened, then you might run into problems.

Code:
Private Sub Command2_Click()

Dim objExcel As Excel.Application
Dim objWorkSheet As Excel.Workbook
Dim objSheet As Excel.Worksheet

Set objExcel = GetObject(, "Excel.Application")
Set objSheet = objExcel.ActiveWorkbook.ActiveSheet

objSheet.Range("A1").Value = "hi"
DoEvents
objExcel.Quit


End Sub