Prevent update of Listview based upon javascript validations

Question

Hi All,

I have a listview control with edit/insert templates. I am using javascript to validate entries for the listview. While the javascript function returns correct true or false values, i want to prevent the listview to be updated if the javascript validation returns a false value. I dont want to use requiredfield validation controls, as i am using a master page also and it tends to cause me issues.

My javascript function is as below:
<script type="text/javascript">
var bProceedFurther = false;
function ValidateBillableYN(id) {
var tbl = id;
var e = tbl.value;
if (e != 'Y' && e != 'N') {
bProceedFurther = false;
return false;
}
else {
return true;
}
if (e == '') {
bProceedFurther = false;
return false;
}
else {
return true;
}
}
function ValidateJobDescription(id) {
var tbl = id;
var e = document.getElementById(tbl).value;
if (e.value == '') {
bProceedFurther = false;
return false;
}
else {
document.getElementById("<%=lblErrorMessage.ClientID%>").innerHTML = "";
return true;
}
}
function ValidateGrid() {
if (ValidateBillableYN(document.getElementById("ContentPlaceHolder1_lvwEstimateJobDetails_txtUpd_Billable_0")) == false) {
document.getElementById("<%=lblErrorMessage.ClientID%>").innerHTML = "* Billable Field Should Either Be Y Or N Only";
document.getElementById(tbl).focus();
return false;
}
if (ValidateJobDescription(document.getElementById("ContentPlaceHolder1_lvwEstimateJobDetails_txtUpd_JobDescription_0")) == false) {
document.getElementById("<%=lblErrorMessage.ClientID%>").innerHTML = "* Job Description Field Cannot Be Blank";
document.getElementById(tbl).focus();
return false;
}
else {
document.getElementById("<%=lblErrorMessage.ClientID%>").innerHTML = "";
return true;
}
}
</script>

Codebehind:
Protected Sub lvwEstimateJobDetails_ItemCommand(sender As Object, e As System.Web.UI.WebControls.ListViewCommandEventArgs) Handles lvwEstimateJobDetails.ItemCommand
Dim txtItemSerialNo As New TextBox
Dim txtJobDescription As TextBox
Dim txtBillable As TextBox
Dim strSQL As String
If (e.CommandName = "Insert") Then
txtItemSerialNo.Text = GetNextItemSerialNo(txtJobNumber.Text)
MsgBox("Next No. = " + txtItemSerialNo.Text)
txtJobDescription = e.Item.FindControl("txtJobDescription")
txtBillable = e.Item.FindControl("txtBillable")
strSQL = "INSERT INTO [EstimateJobs] ([EstimateNumber],[JobDescription],[Billable],[ItemSerialNumber]) VALUES ('" + txtJobNumber.Text + "', '" + txtJobDescription.Text + "', '" + txtBillable.Text + "', " + txtItemSerialNo.Text + ")"
MsgBox(strSQL)
sqlDS_EstimateJobDetails.InsertCommand = strSQL
ElseIf (e.CommandName = "Update") Then
txtItemSerialNo = e.Item.FindControl("txtUpd_ItemSerialNumber")
txtJobDescription = e.Item.FindControl("txtUpd_JobDescription")
txtBillable = e.Item.FindControl("txtUpd_Billable")
strSQL = "UPDATE [EstimateJobs] SET [JobDescription]='" + txtJobDescription.Text + "', [Billable]='" + txtBillable.Text + "' WHERE EstimateNumber='" + txtJobNumber.Text + "' AND ItemSerialNumber='" + txtItemSerialNo.Text + "'"
MsgBox(strSQL)
sqlDS_EstimateJobDetails.UpdateCommand = strSQL
ElseIf (e.CommandName = "Delete") Then
txtItemSerialNo = e.Item.FindControl("txtUpd_ItemSerialNumber")
strSQL = "DELETE FROM [EstimateJobs] WHERE EstimateNumber='" + txtJobNumber.Text + "' AND ItemSerialNumber='" + txtItemSerialNo.Text + "'"
sqlDS_EstimateJobDetails.DeleteCommand = strSQL
End If
End Sub