string salesDocNum = GetCurrentColumnValue("Sales_Doc_Num").ToString();
string salesDocType = GetCurrentColumnValue("Sales_Doc_Type").ToString();
int masterNum = Genframe4.Utils.ConvertToInt32(GetCurrentColumnValue("Master_Num"));

//retrieves the signature for the last PayFabric transaction created for this document
Image img = SalesPad.Ccp.PayFabric.GetLastTransactionSignature(salesDocType, salesDocNum, masterNum); 
//if(img.Tag == null || !img.Tag.Equals("NotFound")) //uncomment to hide "No Signature Found" image.
pictureBox1.Image = img;