Welcome here kpratap! :smile:
There's a big difference between the use/type of signal that usually goes over a CAT5 cable, and raw VGA. So it might help to know what that conversion entails, what kind of technique you're using / what circuit(s) you have on both ends of the cable.
Also: please define "longer length", as far as I know there's VGA cables up to 10 metres, possibly longer. Are we talking 20m? 50m? 100m? More? Why you have VGA signal source & monitor so far apart?