error while casting a column name

Set FormattedValue = CASE 
                         When rg.ReferredFieldType = 'NUM' Then              
                              CAST(#PointedMslValues.Value AS         
                              NUMERIC(18,cAST(rg.ReferredDecimalPoints) )
 
                     --more cases...
END

I am generating a dynamic query, which is giving error.
Actually it requires integer value, while casting not a column name.