Validate form data before saving record?

[adamskiii]

I am starting to learn to use form is access and have created an unbound form because I beleive you have more control over table records. My question is, how do I validate fields on my form first and then once all validation are correct and no errors appear it saves the record? This is currently my code:

Option Explicit
Option Compare Database

Dim connection As New ADODB.connection
Dim part As New ADODB.Recordset

Private Sub Form_Load()
    Set connection = CurrentProject.connection
    part.Open "SELECT * FROM part ORDER BY partID", connection, _
    adOpenDynamic, adLockOptimistic
       
    populateForm
    
    BrowseMode (True)
End Sub


Private Sub populateForm()
    If part.EOF Then
        part.MoveLast
    ElseIf part.BOF Then
        part.MoveFirst
    End If
    
    Me.txtPartId = part.Fields("partId")
    Me.txtCost = part.Fields("cost")
    Me.txtDescription = part.Fields("description")
    Me.txtOnHand = part.Fields("onHand")
    Me.txtOnOrder = part.Fields("onOrder")
    Me.txtListPrice = part.Fields("listPrice")
    Me.cmboVendor = part.Fields("vendorID")
End Sub

Private Sub BrowseMode(value As Boolean)
    
    Me.txtCost.Locked = value
    Me.txtDescription.Locked = value
    Me.txtListPrice.Locked = value
    Me.txtOnHand.Locked = value
    Me.txtOnOrder.Locked = value
    Me.txtPartId.Locked = value
    Me.cmboVendor.Locked = value
    
    Me.cmdFirst.Enabled = value
    Me.cmdLast.Enabled = value
    Me.cmdNext.Enabled = value
    Me.cmdPrevious.Enabled = value
    
    If value Then
        Me.cmdNext.SetFocus
    Else
        Me.txtPartId.SetFocus
    End If
  
    Me.btnAdd.Enabled = value
    Me.btnCancel.Enabled = Not value
    Me.btnEdit.Enabled = value
    Me.cmdExit.Enabled = value
    Me.btnSave.Enabled = Not value
    
End Sub


Private Sub cmdFirst_Click()
    part.MoveFirst
    populateForm
End Sub

Private Sub cmdLast_Click()
    part.MoveLast
    populateForm
End Sub

Private Sub cmdNext_Click()
    part.MoveNext
    populateForm
End Sub

Private Sub cmdPrevious_Click()
    part.MovePrevious
    populateForm
End Sub

Private Sub btnCancel_Click()
    BrowseMode (True)
    part.CancelUpdate
    populateForm
End Sub


Private Sub btnEdit_Click()
    BrowseMode (False)
End Sub

Private Sub btnAdd_Click()
    BrowseMode (False)
    
    part.AddNew
    populateForm
End Sub

Private Sub btnSave_Click()

    part.Fields("partId") = Me.txtPartId.value
    part.Fields("cost") = Me.txtCost.value
    part.Fields("description") = Me.txtDescription.value
    part.Fields("onHand") = Me.txtOnHand.value
    part.Fields("onOrder") = Me.txtOnOrder.value
    part.Fields("listPrice") = Me.txtListPrice.value
    
    part.Update
    BrowseMode (True)
End Sub

Private Sub cmdExit_Click()
    DoCmd.Close
End Sub

In the btnSave_Click() I want it to first check a function called EDIT for all validations. Once all have passed and no errors appear then the form data will be saved. How can I do this? I tried adding the EDIT function:

Private Function edit(editMe As Boolean)
    If (Me.txtCost >= Me.txtListPrice) Then
        MsgBox "ERROR"
    End If
End Function

And then in my btnSave_Click() I added:

Private Sub btnSave_Click()
if edit = True Then
    part.Fields("partId") = Me.txtPartId.value
    part.Fields("cost") = Me.txtCost.value
    part.Fields("description") = Me.txtDescription.value
    part.Fields("onHand") = Me.txtOnHand.value
    part.Fields("onOrder") = Me.txtOnOrder.value
    part.Fields("listPrice") = Me.txtListPrice.value
    
    part.Update
    BrowseMode (True)
End If
End Sub

But this is not working. Any help?

Thanks