How to assign numeric field value in amount field in Sap C4C

Hi All

I am getting a warning when I am trying to assign a numeric field value in custom amount filed on opportunity header. warning is like that Warning1 [Activate] Assignment of the type 'Numeric' to the type 'Amount' is not possible. Please suggest me how I can do this is there any other way. Because I am not able to see numeric data type in the suggestion of data type assignment to my custom field. Please suggest me as soon as possible please.