Hide-Unhide rows on multiple worksheets based on value of a drop down list

Hi All. First post so please bear with me! I have searched and tried various code but cannot find an answer that works.

I have 30 worksheets. On sheet 1 I have a cell, A1 with a drop down list with 3 possible values, A, B or C.

I want to hide or unhide rows 8:12 and 29:42 on sheets 2 through 20 depending on value in cell A1, sheet 1.

e.g. Value in cell A1-Sheet 1 is A, then on sheets 2 to 20 rows 8:12 are hidden and 29:42 are unhidden.

If value is B, then 8:12 are unhidden and 29:42 are hidden.

If value is C then no rows are hidden.

I need this to work every time the user changes the value in cell A1-Sheet

Hope someone can help. I am very new to this so a hint as to where to put it as well would be helpful. Thanks in advance.

Wow, that was quick! Thanks Richard. I will try this tomorrow and let you know how it works out.

Sorry, where should I put this? Should I right click Sheet1 tab, View Code and paste it there?

Worked great, thanks so much