The easiest way to do this is with Material Instances.
Create a UMaterial with a Texture Parameter to serve as the base material. At runtime, create a UMaterialInstanceDynamic and call SetTextureParameterValue to provide a value to your parameter.
If you set your base UMaterial as the material for the mesh section, you can even use the convenience method UPrimitiveComponent::CreateAndSetMaterialInstanceDynamic to create the MID.