Hi - just checking I am barking up the right tree!

I want a view that pulls out records from a base table. The user selects all customers so I have a view with this SQL...

SELECT *;
FROM gen_data!customers;
WHERE Customers.cu_primary BETWEEN ?vp_LowPk AND ?vp_HighPk;
AND DELETED() <> .T.;
ORDER BY Customers.cu_company

That's fine. But can't I use the following SQL and supply a value for vp_Field and vp_Criteria so that it widens the possibilities?

SELECT *;
FROM gen_data!customers;
WHERE Customers.cu_primary BETWEEN ?vp_LowPk AND ?vp_HighPk;
AND ?vp_Field = ?vp_Criteria;
AND DELETED() <> .T.;
ORDER BY Customers.cu_company

I am passing vp_Field = "customers.cu_code" and vp_Criteria as "EMD" (a company code)

This doesn't seem to work and the problem seems to lie with assigning a field.

Am I missing something? Any ideas?