This is not a standard and you need to make some customization. I made this on my projects and this is first help:
You need to create new decimal field od Vendor Card: Customer Balance (LCY).
This field must to be a FlowField, and CalcFormula: Sum("Detailed Cust. Ledg. Entry"."Amount (LCY)" WHERE (Customer No.=FIELD(Customer No.),Initial Entry Global Dim. 1=FIELD(Global Dimension 1 Filter),Initial Entry Global Dim. 2=FIELD(Global Dimension 2 Filter),Currency Code=FIELD(Currency Filter)))
On Customer Card, you need to do the same; create new decimal field Vendor Balance (LCY):
This field must to be a FlowField, and CalcFormula: -Sum("Detailed Vendor Ledg. Entry"."Amount (LCY)" WHERE (Vendor No.=FIELD(Vendor No.),Initial Entry Global Dim. 1=FIELD(Global Dimension 1 Filter),Initial Entry Global Dim. 2=FIELD(Global Dimension 2 Filter),Currency Code=FIELD(Currency Filter)))