static [UMaterialExpression](API\Runtime\Engine\Materials\UMaterialExpression) * CreateMaterialExpressionInFunction ( [UMaterialFunction](API\Runtime\Engine\Materials\UMaterialFunction) * MaterialFunction, [TSubclassOf](API\Runtime\CoreUObject\Templates\TSubclassOf)< [UMaterialExpression](API\Runtime\Engine\Materials\UMaterialExpression) > ExpressionClass, int32 NodePosX, int32 NodePosY )