Forecast graph based on user input

hello some_analyst 

for your first post, input is a table that consisted of user input as your post above.

i am not sure but i assumed you have a way for user to write down their input.

User input should be in a form of table in PBI so you can get that dynamic value into calculation.

the input table in my pbix is a dummy table, so you need to change that table into user input table.

for your second post, in your screenshot, i assumed the negatif value is the problem and i assumed you put in 20 as input.

this probably happens because the value is zero instead of blank in 28 April 2025, so the value becomes negative (0-20=-20).

if this the problem, then lets make a tweak in the DAX by adding not equal to 0.

Pending Forecast = 
var _MaxDate = 
CALCULATE(
MAX('dim_date'[Week Start]),
FILTER(
ALL('Dummy'),
not ISBLANK('Dummy'[Pending])&&
'Dummy'[Pending]<>0
)
)
var _MaxValue = 
MAXX(
FILTER(
ALL('Dummy'),
'Dummy'[Date]=_MaxDate
),
'Dummy'[Pending]
)
var _Input = SELECTEDVALUE('What-If-Parameter'[What-If-Parameter])
Return
IF(
SELECTEDVALUE('Dummy'[Pending])<>BLANK(),
SELECTEDVALUE('Dummy'[Pending]),
_MaxValue -_Input
)

this should take the 1096 value as last value then deducted with 20 in 28 April 2025.

Hope this will help.

Thank you.