Anable to display currency field -smart forms

Hai,

I am new to ABAP ,I am trying to display PO using smart form but I am unable to display currency field (netpr).there is no syntax error or runtme error but when i press print preview button

' Reference field X_EKPO-NETPR unknown in form'.

message is displayed.

can any one help me.

thanks in advance

regards

Swetha Singh