Replacing the value in different sheets but same cell by adding a number

Hi,
I have a workbook having different sheets. I want to change the value of cell B4 in all sheets by adding 6. e.g.
Sheet1 B4 old value "lab-wn-as-hue-0256" New value "lab-wn-as-hue-0262".
Sheet2 B4 old value "lab-wn-as-hue-0262" new value "lab-wn-as-hue-0268".
Sheet3 B4 old value "lab-wn-as-hue-0260" new value "lab-wn-as-hue-0266".

Any body can help me .
Thanks in advance
Atiq