I do not know a way of going directly to a field in a variable in meta code, but if you +++define your field, you can add meta code to only generate the If statement when the field is equal.
+++define Field: InvoiceStatus
+++define +CurrentField
+for each field VariableL
+++set value to current +CurrentField
+if eq +CurrentField, InvoiceStatus
+for each field value.
If you only want the field values, without caring which variable it is in, it is easier still.
+++define Field: InvoiceStatus
+for defined value Field: InvoiceStatus
To get the values themselves
+for each property target fld value val
OR to get the value triple
+for each property Fld Value val