Add this code to a standard module and call it from code in your form like:
ClearListBox Me.lboDepts
Sub ClearListBox(pctlListBox As ListBox)
'============================================================
' Purpose: clear all selection from a list box control
' Programmer: Duane Hookom
' Called From: Multiple
' Date: 2/21/2003
' Parameters: list box object
'============================================================
On Error GoTo ClearListBox_Err
Dim strErrMsg As String 'For Error Handling
Dim varItem As Variant
For Each varItem In pctlListBox.ItemsSelected
pctlListBox.Selected(varItem) = False
Next
ClearListBox_Exit:
On Error Resume Next
Exit Sub
ClearListBox_Err:
Select Case Err
Case Else
strErrMsg = strErrMsg & "Error #: " & Format$(Err.Number) &
vbCrLf
strErrMsg = strErrMsg & "Error Description: " & Err.Description
MsgBox strErrMsg, vbInformation, "ClearListBox"
Resume ClearListBox_Exit
End Select
End Sub