Effective Interest Calculation for Interest Rate Insturment

Hi,

We are using money market instrument ( Product type 55A) for processing external debt/bonds.

We are using other flow type(90) to map any upfront fees or costs which will be amortized over the tenure of the debt thru TBB4. The flow type has an accrual flow type associated.

Now there is a requirement to amortize these costs using effective interest rate ( actual interest rate X net bookvalue of debt).

I have tried to activate effective interest in the product type and relevant flow configuration and system shows calculates some effective rate ( not sure how, selected Linear method)

But when I run TBB4 the amortization amount is still straight line fixed amount over the remaining tenure.

please let me know what I am missing here.

P.s: The flow type is set up with  flow category "90" with cal.category as Fixed .

Thanks,

Vamsi