Multiple Condition Message Box - Invalid Range

VBA code. I think I need a worsksheet change event. Here is what I'm looking for:

If cell K1 = 3 and if the value of any cell in column A is < 80000 or is > 86666, or if the five digit number begins with an alpha, then a msg box will pop up stating "Invalid range".

More background:
The user will be manually inputting 5 digit numbers into column A, but if they've selected cell K1 to equal 3 from a dropdown menu (which the user also does), then values entered that are less than 80000 or greater than 86666 are 'out of range', and the user should be alerted and if possible the number they entered gets cleared.

Additionally, some of the numbers the user could type in might begin with an alpha prefix, such as "G1234" - these would also be considered out of range when K1=3, so if the conditional statement could also recognize this it would be useful.

Column A will be blank until the user types in the 5 digit number, so the code only needs to trigger if the number typed into a cell in column A is outside of the aforementioned range.

So to sum it up once again, I'm looking for a msgbox (and clear cell) if the following criteria is simultaneously met-
*If K1 = 3 (meaning that K1 equaling anything other than 3 wouldn't cause the msgbox)
*And values typed in column A are less than 80000 or are greater than 86666, or begin with an alpha (meaning that values typed in between 80000 - 86666 wouldn't cause the msg box.)