is there a simple way make a condition true on a rising edge on an input

[Ingvar]

Since you want to use PortB.0 you can check the interruptflag.

OPTION_REG.6 = 1       ' rising edge
INTCON.1 = 0           ' reset the interruptflag

IF INTCON.1 = 1 THEN
   INTCON.1 = 0        ' reset the interruptflag
   ' your code
ENDIF