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To answer your question – declare your variables once as undefined at the start of your code.

once q12 = undefined
once m10 = undefined
once m40 = undefined
once w10 = undefined
once w40 = undefined
once d50 = undefined
once d200 = undefined

If (date-date[1])=1 OR (date[1]-date[2])=1 Then
a=1 // 1 signals Daily timeframe
Endif
If (date-date[1])=7 OR (date[1]-date[2])=7 Then
a=7 // 7 signals Weekly timeframe
Endif
If (date-date[1])=30 OR (date[1]-date[2])=30 Then
a=30 // 30 signals Monthly timeframe
Endif
If (date-date[1])=299 OR (date[1]-date[2])=299 Then
a=100 // 100 signals Quarterly timeframe
Endif
If (date-date[1])>9500 Then
a=200 // 200 signals Annual timeframe
Endif
 
 
If (a=100) Then
 
Q12= Average[12](close)


Elsif (a=30) Then
 
M10= Average[10](close)
M40= Average[40](close)

 
Elsif (a=7) Then
 
W10= Average[10](close)
W40= Average[40](close)
 
Elsif (a=1) Then
 
D50= Average[50](close)
D200= Average[200](close)
 
EndIf

return Q12 COLOURED(0,0,255) AS "12 Quarter SMA",M10 COLOURED(230,230,250) AS "10 Month SMA",M40 COLOURED(0,0,255) AS "40 Month SMA", W40 COLOURED(0,0,255) AS "40 Week SMA",W10 COLOURED(230,230,250) AS "10 Week SMA", D50 COLOURED(230,230,250) AS "50 Day SMA", D200 COLOURED(0,0,255) AS "200 Day SMA"

2 snippets for timeframe detection with code: https://www.prorealcode.com/topic/determine-the-charts-time-frame-in-a-program/#post-105538