Helena,

Skimask is right.

There are many people looking for ready-cooked cake around here.

Here is some hints for you to show us whether you can do something on your own and continue on this code.

Code:
Btn1   VAR PORTB.0      'First Button
Led1   VAR PORTB.4      'First Led
TenMin CON 100          'A constant value for Ten-Minute timing condition.
TIME   VAR WORD         'Variable for Timing   

IF Btn1 = 0 THEN
   WHILE Btn1=0 : WEND    'Wait for finger release.
   TIME = TenMin          'Set initial timing value.
   HIGH Led1              'Activate first LED.
   WHILE TIME > 0         'Set a timing condition.
      PAUSE 6000          'Wait for 6 second.
      TIME = TIME - 1     'Decrement "initial" timing value.
   WEND                  'Total of TenMin*6000ms passed; 600,000ms = 10minutes.
   LOW Led1               'De-Activate first LED.  
ENDIF