Use texture sequence

Basically, you can't use keyframe with MayaManCustomShader.
Instead, you have to use Expression.

//Maya expression ColorMapNum = frame;

And this is a part of Renderman shader.
If texture path is
C:\project\textureA.0001.tif
You can code like this.

TextureName = format("%s.%04d.%s", TextureName, TextureNum, TextureExt); Color=color texture(TextureName, X, Y, "blur" ,Blur ,"fill" , -1, "alpha", Alpha);

TextureName = "C:\project\textureA"
TextureNum will come from Maya's expression
TextureExt = "tif"

I defined texture offset as attribute, and coded like

TextureNum += TextureOffset;

But this one couldn't work at frame 1.
I couldn't solve this issue.
So I added offset value in Maya's expression instead.