Hiding/Unhiding Rows Based on Dropdown Box

Hello all, this issue has been stumping me for the longest time and I would greatly appreciate your collective help.

Situation:
I have a worksheet that needs to hide/unhide rows based on a dropdown box (form control). The dropdown box has 3 choices. Depending on the value of the dropdown box, it will hide certain rows. However, the worksheet must be protected because there are formulas within Excel throughout the sheet and as these are being designed for another group, I'd like to have them protected to prevent accidental errors.

Error:
When the sheet is protected and I change the dropdown box (for example from selection 1 to selection 3), I receive a run-time error: 1004. Unable to set the Hidden property of the Range class.

Code:

'Select number of issues
Sub DropDown_Number_Issue()

    Select Case Range("J4").Value
    
        '1 investigation
        Case 1
            Call Investigation_2_Close
            Call Investigation_3_Close

        '2 investigations
        Case 2
            Call Investigation_2_Open
            Call Investigation_3_Close
        
        '3 investigations
        Case 3
            Call Investigation_2_Open
            Call Investigation_3_Open
End Select
End Sub


'Open investigation 2
Sub Investigation_2_Open()

    Rows("57:74").Hidden = False
    Range("H57").Value = "=SUM(H58:H61)"
    Range("I57").Value = "=SUM(I58:I61)"
    Range("H64").Value = "=SUM(H65:H72)"
    Range("I64").Value = "=SUM(I65:I72)"
End Sub

This is the partial code used. The bolded line is highlighted after clicking on debug.

Any help would be great.

Attachment included to help. The error is encountered any time the dropdown box is changed.

Hello SubParLlama,

Welcome to the Forum.

Try this,

'Open investigation 2
Sub Investigation_2_Open()

    Sheets("Name").Unprotect ("Password")
    Rows("57:74").Hidden = False
    Range("H57").Value = "=SUM(H58:H61)"
    Range("I57").Value = "=SUM(I58:I61)"
    Range("H64").Value = "=SUM(H65:H72)"
    Range("I64").Value = "=SUM(I65:I72)"
    Sheets("Name").Protect ("Password")

End Sub

Where Sheets("Name" = the actual sheet name, And ("PassWord" = the actual password for the Sheet, if a password does exist.

Also see the "Please consider" note at the bottom of this post.

And? Where is your attachment?

Hello SubParLlama,

Try the attached WorkBook now.

Also see the "Please consider" note at the bottom of this post.

Hello SubParLlama,

You are welcome.

Thank you for the Rep.

You have done a great piece of work, and you don't need to "learn" very hard of how your issue was resolved.

The DropDownBox is linked to Cell G4, and G4 was not "Unlocked" before protecting the Sheet.