​@bobbytherbs  Hi,
you can follow below approach hope it will work.
Note: Generated from AI

 

DAC Extension (Customer)

Create a DAC Extension for Customer.

using PX.Data;
using PX.Objects.AR;
using PX.Objects.CR;
using PX.Objects.CM;

namespace Customization
{
    public class CustomerExt : PXCacheExtension<Customer>
    {
        #region UsrOpenInvoices

        [PXDecimal]
        [PXUIField(DisplayName = "Open Invoices", Enabled = false)]
        public decimal? UsrOpenInvoices { get; set; }

        public abstract class usrOpenInvoices : PX.Data.BQL.BqlDecimal.Field<usrOpenInvoices> { }

        #endregion
    }
}

Graph Extension (CustomerMaint)

Now calculate the value.

using PX.Data;
using PX.Objects.AR;
using PX.Objects.AR.Standalone;

public class CustomerMaint_Extension : PXGraphExtension<CustomerMaint>
{
    protected void _(Events.RowSelected<Customer> e)
    {
        if (e.Row == null) return;

        decimal totalOpenInvoices = 0;

        foreach (ARInvoice inv in PXSelect<
            ARInvoice,
            Where<
                ARInvoice.customerID, Equal<Required<ARInvoice.customerID>>,
                And<ARInvoice.status, Equal<ARDocStatus.open>,
                And<ARInvoice.docType, Equal<ARDocType.invoice>>>>>
            .Select(Base, e.Row.BAccountID))
        {
            totalOpenInvoices += inv.CuryDocBal ?? 0;
        }

        CustomerExt ext = e.Row.GetExtension<CustomerExt>();
        ext.UsrOpenInvoices = totalOpenInvoices;
    }
}

Add Field to UI

Open Customization Project → Screens → Customers (AR303000)

Add field to the Balance area.

Result

Customer screen will show:

Field	Value
Balance	800
Open Invoices	1000
Prepayment Balance	-200

https://help.acumatica.com/(W(5))/Wiki/ShowWiki.aspx?pageid=5a2bddc7-dd58-4de4-a9f5-f4d5ce073b77