Help required please!

Based on the value I return in cell H37 in a worksheet called "Promotion
Form", I need to be able to unhide a specifc row. So, to be exact....

if cell H37 = TRUE, I want row 28 to unhide (but row 29 which is also hidden
should remain hidden)
if cell H37 = FALSE, I want row 29 to unhide (but row 28 should remain hidden)
if cell H37 is blank, I want rows 28 and 29 to remain hidden.

I have tried writing various bits of code but have had no success.

Can anybody help me?

Many thanks