Creating SumIf function in SQL Server 2012

Question

I need some help building a SQL Server function that acts as a SumIf in Excel, for example

SumIF(Fees.Fee_Amount, Fees.Type ='Services' and Fees.Fee_Code = 'B01')

so the item that would be summed if it is a Fees.Fee_Amount and the where part is Fees.Type ='Services' and Fees.Fee_Code = 'B01'

Syntax would be SumIf(TableName.ColumnName, Criteria), the function would return the total.