Manual control of reflection rotation

I have a simple shader with transparency and a cubmap for reflections and need control over the rotation of the reflection manually (in the inspector) rather than just it be controlled by the camera position/object orientation - the camera and object are static while the reflection rotation needs to change.

There are a few related questions and answers I’ve found but none quite achieve the control I’m looking for.

The shader as it stands is:

Shader "Custom/3DGUIGlassFront" {

	Properties {

		_MainTint ("Diffuse Tint", Color) = (1,1,1,1)
		_Cubemap ("CubeMap", CUBE) = ""{}
		_ReflAmount ("Reflection Amount", Range(0.01, 1)) = 0.5


	SubShader {

		Tags { "RenderType"="Transparent" }
		LOD 200
		#pragma surface surf Lambert alpha

		float4 _MainTint;
		samplerCUBE _Cubemap;
		float _ReflAmount;

		struct Input {
			float2 uv_MainTex;
			float3 worldRefl;

		void surf (Input IN, inout SurfaceOutput o) {
			half4 c =  _MainTint;
			o.Emission = texCUBE (_Cubemap, IN.worldRefl).rgb * _ReflAmount;
			o.Albedo = c.rgb;
			o.Alpha = c.a;




	FallBack "Diffuse"


Not the most elegant solution but perhaps the simplest; I’ve simply parented the reflective objects to the camera and rotate the camera - gives the same effect and controlling the camera orientation is simple.