I'm not sure I understand the question. Everything you view on screen is RGB because that's what your monitor produces. The CMYK values are converted on the fly to the RGB equivalents.
Depending on what you're doing - it probably makes more sense to create the document in RGB.
That way you can view it in RGB on screen - and printers can do a conversion to CMYK from there.
Normally you will place in you InDesign document RGB anyway. (I would not recommend to use CMYK images for print in an INDD file.) If you create a PDF for Print you should export it according to the requirement of the printer, this is often a CMYK file you can create direktly with the export PDF functionality. For screen users you should export a PDF file from the same INDD in sRGB for web, it could be done with the PDF Expot for Interactive.
still prints in CYMK but when you view it on the computer it's RGB.
Use the PDF/X-4 preset